Abstract: A simulation test method on electric-optic countermeasure to real laser seekers was proposed to get high reliability of real laser seeker and sample quality of simulation, and the major error factor was found. It was diagrammatic how the process of test worked, and the steps of test were given. According to the characteristic of diffuse reflection target and direct irradiated equipment, the models of laser energy density for diffuse reflection target and direct irradiated equipment at the point of laser seeker were established, and the error distribution principle was analyzed numerically. Besides, it was defined how to get the valid distance with error. The real jamming tests were performed to a real seeker by an electro- optic countermeasure system. The conclusion is that the jamming to laser guided weapon was valid by the electro-optic countermeasure system, and the valid distance also was given. The method was proved to be effective by the tests.