In the simulation test of IR tracing and searching system or IR warning system by digital image injecting, IR dynamic scenes simulation is the core technology, and optic system effect simulation is the important part of IR dynamic scenes simulation. Since the object is incoherent IR imaging system, imaging effect and image disperse or energey disperse effect in energey domain are only considered for optic system effect. In general, optic system quality can described by MTF. Point-expanded function can be calculated using MTF, and optic system effect model can be established based on point-expanded function. So long as MTF is accurate, the fidelity of optics system effect model established by this way can be guaranteed.