The light leak from different roughness surface reflected was studied. The bidirectional reflectance distribution function model is established by correcting Torrance - Sparrow model, and the influence factors on the bidirectional reflectance distribution function are numerical calculated. The mathematical model and numerical results are verified by experiments. The main factors affecting the reflected information are the mirror reflection, the diffuse reflection and the absorption of medium, which the mirror reflection includes the reflecting reflectivity of objects, the probability distribution function of micro-elements on reflection surface, the shading factors caused by incident ray incident angle and reflection angle. The main influencing factors is mirror reflection. When the incident angle and roughness are selected and reflection angle is varied from 0 to π/2, reflecting surface bidirectional reflectance distribution function is shown as Gaussian distribution based on the mirror reflection angle under the condition of small reflection angle. If the reflection angle is greater than 1.4 rad, reflective surface bidirectional reflectance distribution function value has increased dramatically and performed a deformation of Gaussian distribution. If the reflection angle of the mirror is selected to receive the reflection information, the bidirectional reflection distribution function of reflecting surface decreases monotonically and changes rapidly with the increase of the roughness of reflecting surface. When the roughness is greater than 0.3, the bidirectional reflection distribution function is close to 0.