diff --git a/mmengine/utils/package_utils.py b/mmengine/utils/package_utils.py
index 8abf4965..b224625f 100644
--- a/mmengine/utils/package_utils.py
+++ b/mmengine/utils/package_utils.py
@@ -24,7 +24,13 @@ def is_installed(package: str) -> bool:
         get_distribution(package)
         return True
     except pkg_resources.DistributionNotFound:
-        return importlib.util.find_spec(package) is not None
+        spec = importlib.util.find_spec(package)
+        if spec is None:
+            return False
+        elif spec.origin is not None:
+            return True
+        else:
+            return False
 
 
 def get_installed_path(package: str) -> str:
@@ -54,20 +60,12 @@ def get_installed_path(package: str) -> str:
         if spec is not None:
             if spec.origin is not None:
                 return osp.dirname(spec.origin)
-            # For namespace packages, the origin is None, and the first path
-            # in submodule_search_locations will be returned.
-            # namespace packages: https://packaging.python.org/en/latest/guides/packaging-namespace-packages/  # noqa: E501
-            elif spec.submodule_search_locations is not None:
-                locations = spec.submodule_search_locations
-                if isinstance(locations, list):
-                    return locations[0]
-                else:
-                    # `submodule_search_locations` is not subscriptable in
-                    # python3.7. There for we use `_path` to get the first
-                    # path.
-                    return locations._path[0]  # type: ignore
             else:
-                raise e
+                # `get_installed_path` cannot get the installed path of
+                # namespace packages
+                raise RuntimeError(
+                    f'{package} is a namespace package, which is invalid '
+                    'for `get_install_path`')
         else:
             raise e
 
diff --git a/tests/test_utils/test_package_utils.py b/tests/test_utils/test_package_utils.py
index c23d1c31..bed91b6c 100644
--- a/tests/test_utils/test_package_utils.py
+++ b/tests/test_utils/test_package_utils.py
@@ -1,7 +1,9 @@
 # Copyright (c) OpenMMLab. All rights reserved.
 import os.path as osp
 import sys
-from pathlib import Path
+
+import pkg_resources
+import pytest
 
 from mmengine.utils import get_installed_path, is_installed
 
@@ -10,32 +12,26 @@ def test_is_installed():
     # TODO: Windows CI may failed in unknown reason. Skip check the value
     is_installed('mmengine')
 
-    # package set by PYTHONPATH
-    assert not is_installed('py_config')
-    sys.path.append(osp.abspath(osp.join(osp.dirname(__file__), '..')))
-    assert is_installed('test_utils')
+    # If there is `__init__.py` in the directory which is added into
+    # `sys.path`, the directory will be recognized as a package.
+    PYTHONPATH = osp.abspath(
+        osp.join(osp.dirname(__file__), '..', '..', 'mmengine'))
+    sys.path.append(PYTHONPATH)
+    assert is_installed('optim')
     sys.path.pop()
 
 
-def test_get_install_path(tmp_path: Path):
+def test_get_install_path():
     # TODO: Windows CI may failed in unknown reason. Skip check the value
     get_installed_path('mmengine')
 
     # get path for package "installed" by setting PYTHONPATH
-    PYTHONPATH = osp.abspath(osp.join(
-        osp.dirname(__file__),
-        '..',
-    ))
+    PYTHONPATH = osp.abspath(osp.join(osp.dirname(__file__), '..'))
+    PYTHONPATH = osp.abspath(
+        osp.join(osp.dirname(__file__), '..', '..', 'mmengine'))
     sys.path.append(PYTHONPATH)
-    res_path = get_installed_path('test_utils')
-    assert osp.join(PYTHONPATH, 'test_utils') == res_path
+    assert get_installed_path('optim') == osp.join(PYTHONPATH, 'optim')
+    sys.path.pop()
 
-    # return the first path for namespace package
-    # See more information about namespace package in:
-    # https://packaging.python.org/en/latest/guides/packaging-namespace-packages/  # noqa:E501
-    (tmp_path / 'test_utils').mkdir()
-    sys.path.insert(-1, str(tmp_path))
-    res_path = get_installed_path('test_utils')
-    assert osp.abspath(osp.join(tmp_path, 'test_utils')) == res_path
-    sys.path.pop()
-    sys.path.pop()
+    with pytest.raises(pkg_resources.DistributionNotFound):
+        get_installed_path('unknown')