Embodiments of the present disclosure disclose a method and an apparatus for determining a planar surface. A specific embodiment of the method comprises: determining, from obtained images of the environment that include a to-be-determined planar surface, feature points belonging to the to-be-determined planar surface; judging whether the number of the feature points belonging to the to-be-determined planar surface is smaller than a preset number threshold; if yes, generating first prompt information for prompting a user to add feature points on the to-be-determined planar surface; obtaining at least two first images including the added feature points; and in response to the number of the feature points belonging to the to-be-determined planar surface in the first images being no less than the preset number threshold, reconstructing the to-be-determined planar surface based on the first images so as to determine a location and an orientation of the to-be-determined planar surface. This embodiment implements reconstruction of a weakly-textured or texture-less planar surface.