Polarization detecting technology has become an important means of detection, the research on its detecting mechanism has important theoretical significance and practical value, it will guide the practical application and results analysis of visible and near-infrared polarization detection. With the rapid development of micro-lens array technology, micro-polarizer array focal plane has become a new type of detector. A lot of literature on the study of the micro-lens array technology, micro-polarizer array focal plane is only involved in design and the optical performance analysis, but the exact theoretical formula for the noise equivalent degree of linear polarization(NeDoLP) was not given. The factors, such as focal plane array size, polarizer extinction ratio(ER), pixel crosstalk, and processing algorithms were analyzed aiming to micro-polarizer array focal plane. The accurate theoretical expression of the noise equivalent degree of linear polarization was given, and simulation analysis was completed with computer. The study has important guiding for improving the performance of the micro-polarizer array focal plane.