Effective medium theory is of great importance for using the artificial microstructure materials to extend the optical parameters. In this article, we develop a new kind of effective medium theory for artificial microstructures with nonlocal effects, like photonic crystals, which we name the pseudo-local effective medium theory. The optical properties of the pseudo-local effective medium are described by effective local permittivity ${\overleftrightarrow \varepsilon ^{\rm{p}}}\left( \omega \right)$ and permeability ${\overleftrightarrow \mu ^{\rm{p}}}\left( \omega \right)$ , together with an additional wave vector ${{{k}}_a}$ . We find that the pseudo-local medium exhibits a unique blend of local and nonlocal characteristics. On the surface normal to ${{{k}}_a}$ , the pseudo-local medium is optically equivalent to its local medium counterpart. While on the surface parallel to ${{{k}}_a}$ , the abnormal wave phenomena induced by inherent nonlocality, such as negative refraction and total reflection, may occur. Furthermore, it is found that a $\text{π}$ phase shift is added to transmission wave through the pseudo-local medium composed of odd number of unit cells under all incident angles. Based on this unique feature, an all-angle phase grating is proposed. Our work opens a route towards the advanced optical devices based on the pseudo-local effective media.