The infrared detector module is the key device of target detection and imaging system and it′s spatial resolution directly affects imaging quality of detection system. When evaluating the spatial resolution of detector modules, researchers usually adopt modulation transfer function(MTF), which optical crosstalk is the crucial factor to impact MTF. A set of infrared micron-spot test system was introduced whose optical dispersion diameter can achieve to 30 μm in order to test the line spread functions(LSF) of detectors with different structures to acquire optical crosstalk data. The results show that the profile of overlap electric region is photosensitive, which is the main factor to cause widening LSF, secondary peak and so on. The results provide reference for optical crosstalk design of infrared detector modules.