diff --git a/mmcls/apis/inference.py b/mmcls/apis/inference.py
index 4a2160424..e1e8a0be3 100644
--- a/mmcls/apis/inference.py
+++ b/mmcls/apis/inference.py
@@ -1,16 +1,14 @@
 # Copyright (c) OpenMMLab. All rights reserved.
-from typing import Union
+from typing import TYPE_CHECKING, Union
 
 import numpy as np
 import torch
-from mmengine.dataset import Compose, default_collate
-from mmengine.model import BaseModel
-from mmengine.registry import DefaultScope
 
-import mmcls.datasets  # noqa: F401
+if TYPE_CHECKING:
+    from mmengine.model import BaseModel
 
 
-def inference_model(model: BaseModel, img: Union[str, np.ndarray]):
+def inference_model(model: 'BaseModel', img: Union[str, np.ndarray]):
     """Inference image(s) with the classifier.
 
     Args:
@@ -21,6 +19,11 @@ def inference_model(model: BaseModel, img: Union[str, np.ndarray]):
         result (dict): The classification results that contains
             `class_name`, `pred_label` and `pred_score`.
     """
+    from mmengine.dataset import Compose, default_collate
+    from mmengine.registry import DefaultScope
+
+    import mmcls.datasets  # noqa: F401
+
     cfg = model.cfg
     # build the data pipeline
     test_pipeline_cfg = cfg.test_dataloader.dataset.pipeline
diff --git a/mmcls/apis/model.py b/mmcls/apis/model.py
index 11407cc0c..a4882102b 100644
--- a/mmcls/apis/model.py
+++ b/mmcls/apis/model.py
@@ -8,18 +8,14 @@ from pathlib import Path
 from typing import List, Union
 
 from mmengine.config import Config
-from mmengine.runner import load_checkpoint
-from mmengine.utils import get_installed_path
 from modelindex.load_model_index import load
 from modelindex.models.Model import Model
 
-import mmcls.models  # noqa: F401
-from mmcls.registry import MODELS
-
 
 class ModelHub:
     """A hub to host the meta information of all pre-defined models."""
     _models_dict = {}
+    __mmcls_registered = False
 
     @classmethod
     def register_model_index(cls,
@@ -56,6 +52,7 @@ class ModelHub:
         Returns:
             modelindex.models.Model: The metainfo of the specified model.
         """
+        cls._register_mmcls_models()
         # lazy load config
         metainfo = copy.deepcopy(cls._models_dict.get(model_name.lower()))
         if metainfo is None:
@@ -77,12 +74,16 @@ class ModelHub:
 
         return config_path
 
-
-# register models in mmcls
-mmcls_root = Path(get_installed_path('mmcls'))
-model_index_path = mmcls_root / '.mim' / 'model-index.yml'
-ModelHub.register_model_index(
-    model_index_path, config_prefix=mmcls_root / '.mim')
+    @classmethod
+    def _register_mmcls_models(cls):
+        # register models in mmcls
+        if not cls.__mmcls_registered:
+            from mmengine.utils import get_installed_path
+            mmcls_root = Path(get_installed_path('mmcls'))
+            model_index_path = mmcls_root / '.mim' / 'model-index.yml'
+            ModelHub.register_model_index(
+                model_index_path, config_prefix=mmcls_root / '.mim')
+            cls.__mmcls_registered = True
 
 
 def init_model(config, checkpoint=None, device=None, **kwargs):
@@ -109,10 +110,15 @@ def init_model(config, checkpoint=None, device=None, **kwargs):
         config.merge_from_dict({'model': kwargs})
     config.model.setdefault('data_preprocessor',
                             config.get('data_preprocessor', None))
+
+    import mmcls.models  # noqa: F401
+    from mmcls.registry import MODELS
+
     model = MODELS.build(config.model)
     if checkpoint is not None:
         # Mapping the weights to GPU may cause unexpected video memory leak
         # which refers to https://github.com/open-mmlab/mmdetection/pull/6405
+        from mmengine.runner import load_checkpoint
         checkpoint = load_checkpoint(model, checkpoint, map_location='cpu')
         if not model.with_head:
             # Don't set CLASSES if the model is headless.
@@ -216,6 +222,7 @@ def list_models(pattern=None) -> List[str]:
          'resnet50_8xb256-rsb-a2-300e_in1k',
          'resnet50_8xb256-rsb-a3-100e_in1k']
     """
+    ModelHub._register_mmcls_models()
     if pattern is None:
         return sorted(list(ModelHub._models_dict.keys()))
     # Always match keys with any postfix.
diff --git a/requirements/runtime.txt b/requirements/runtime.txt
index 9f814b0ea..e0acc881b 100644
--- a/requirements/runtime.txt
+++ b/requirements/runtime.txt
@@ -1,4 +1,5 @@
 matplotlib
+modelindex
 numpy
 packaging
 rich