A new opto-electronical network with the function of adaptive thresholding is proposed. According to the input modes, it can adaptively adjust the threshold value of the system through competition among the net units. As a result, the threshold is always equal to the maximum input. So the function of WAT (winner-take-all) is achieved. The system is mainly composed of a-Si PIN photo-electrical detector and WTA electrical network. With parallel processing, it permits rapid response, high sensitivity, better addressing capability, simpler structure and stable performance, etc. It can be conveniently applied to opto-electronical systems such as adaptive thresholding, correlation peak detecting and associative memory. A specific network with 36 units is analyzed and the experimentce results are presented.