Aiming at the problem that the small target was hard to be detected from infrared image in single craft-s infrared search and track (IRST) system under disorder background and great yawp situation, due to the limit of detecting distance and precision, the dual-craft coordinated detecting of the same target area at the same time was used. Then the process of images matching and fusion was conducted, in which a multi-rule algorithm that the high frequency based on area and the low based on pixel was adopted, and a target detecting method based on wavelet transform and edge information token was proposed after the fusion. The emulation experiment shows that the multi-rule fusion algorithm can improve the evaluation index of images quality by from 30% to 50%, and the method can eliminate false targets from 7 to 3，filter disturbing waves, reduce the false alarm rate and detect small targets efficiently and accurately.