In order to decrease the influence resulted from the fluctuation of moving targets RCS in the flight process, this paper gives several common target RCS fluctuation models based on the analysis of RCS characteristics, then builds a proper model considering the concrete circumstances of virtual targets, and makes a detailed analysis of the effect that the long dwell signal combats fluctuating targets. Compared with the conventional radar signal, the long dwell signal could smooth the RCS of fast fluctuating targets under certain fluctuant frequency range and decrease a series of influence resulted from fluctuating targets through analyzing the results of long dwell signal sampling. Finally, the long dwell signal could implement stable tracking effectively in the perspective of analyzing stable tracking range. The simulation results also show that the long dwell signal has a good property in anti-target fluctuation.