Abstract: Aimed at the limit of traditional target detection research based on RCS statistical model, a new method of calculation on detection probability based on primitive RCS data has been proposed. Firstly, two sets of RCS data under tracks of level flight and level swerve maneuver are obtained by FEKO. And then they are fitted with Chi-2 distribution to validate the problem of model fitting after dealt with statistical analysis. Secondly, a new detection probability calculation model containing both distance and RCS is gained via deduction between RCS and echo range. Finally, the detection probability of mobile target at random time under the established two tracks is simulated utilizing the obtained RCS data. The result indicates the reality that distance and RCS influence detection probability together. The method proposed can offer theory support on simulative confront between radar and stealth target and improve radar’s detection performance and tactical indexes.