Abstract: Due to the insufficient analysis on the specific impact of dual stealth aircraft formation self-defense coherent jamming on monopulse radar and the lack of rational evaluation to error effectiveness, considering the random characteristics of the phase difference between the dual aircraft echoes, a dual stealth aircraft coherent jamming model and an angle error evaluation model were established. Setting the track of dual aircraft and extracting the dynamic RCS of dual aircraft, a calculation formula was deduced for the random angle error caused by the dual aircraft coherent jamming under the echo. And then several processes were carried out including solving the first order digital characteristics of random angle errors, establishing the angle error validity evaluation criterion according to the miss distance, and calculating the validity probability of angle error. Simulation results show that the angle error caused by the dual stealth aircraft coherent jamming is relatively larger and the random fluctuation is weak. The stable jamming effect and large error validity probability to radar can insure the security of formation penetration.