With the stochastic differential in radar jamming signal processing, the noise frequency modulation signal was particularly analyzed in this paper. The Fokker-Planck equation, which is used to describe the processing of noise frequency modulation signal, was presented. According to the Motion-Group Fourier Transform, the partial differential equation was converted into the variable coefficient homogenous linear differential equations. With the Peano-Baker series, the solutions and the probability density function of noise frequency modulation were given