In order to improve the survival probability of missiles in attacking process,the trajectory of it should be designed properly.Based on the monopulse radar performance indexes,the RCS values of a cone-spheroid shaped warhead are calculated out by using electromagnetic computing software.And detection probabilities of the warhead at different launch angles and different altitudes are computed out respectively.Numerical simulation results show that there are two areas where detection probability stays at a high level.One is that the launch angle is in the range of 0°~90°,while warhead altitude locates in 20~60 km;the other is launch angel is in the range of 270°~360° while warhead altitude locates in 20~60 km.The detection probability keeps at al low level when the launch angle is in the range of 90° to 270°.It comes to us that launch angle of missile should be selected carefully to keep the detection probability stay at a lower level.