Basing on the analysis and simulation of a-Si TFT/PIN coupled unit, we obtained optimized design for structure parameters of detecting unit and material parameters suitable for detecting spectrum. In order to satisfy the low-temperature process of a-Si TFT and a-Si PIN, polyimide (PI) film has been used as the insulator in the TFT/PIN array. We have investigated process compatibility between a- Si TFT and a-Si PIN preparation and fine pattern for low- temperature PI film. As a result, we obtained 2D a-Si TFT/PIN image sensor (6 X 12 pixels) which has signal readout and sensor function. We tested and analyzed its static characteristic. The results indicate that the characteristics of PIN photodiode and TFT switch are better, and the performance of illumination response of the 2D image sensor is good. We propose to apply the image sensor into neural network system in order to decrease cross-coupling between pixels and increase parallel processing rate.