A theoretical model has been put forward to describe the dynamic properties of photoinduced anisotropy in photochromic diarylethene/PMMA film. The kinetic curves of molecule concentration, photoinduced dichroism and birefringence are calculated under the condition of excitation by linearly polarized light. The results show that the color molecule concentration decreases with the increase of the excitation exposure until the saturation point is reached. The photoinduced anisotropy increases to a maximum and then decreases with the exposure increasing. The optimal exposure is 260 J/cm2. Using the orthogonal polarization detection, the transmittance of probe beam reflecting the anisotropy is measured. The experimental result and the theoretical calculation are essentially consistent.