In the mobile space optical communication, the fast capture of laser spot center is very important, but it is difficult to satisfy the requirement by using the traditional grayscale gravity center algorithm.In this paper, an optimization scheme is proposed.Filtering de-noising and adaptive binaryzation threshold processing are added before calculating the spot center, which can effectively improve the anti-interference performance of the system.The speed and accuracy of spot center detection are improved by coarse identification of spot center and gravity center calculation.Experiments show that, compared with the traditional grayscale gravity center algorithm, the improved scheme proposed here increases the measurement accuracy and operation speed by an order of magnitude, and has stronger anti-interference ability.