Abstract: An intelligent eavesdropper may easily intercept the frequency transition relations if a constant G function is used in Differential Frequency Hopping (DFH) system because of the poor 2-dimensional continuity of constant DFH sequence. To solve the problems, this paper puts forward a DFH code generator construction method which combines G function with PN sequence in a DFH system. The 2-Dimensional (2D) continuity performance of generated DFH patterns between constant G function and DFH code generator are tested and compared. The Symbol Error Rate (SER) performance in AWGN is analyzed in theory, and the corresponding simulation results are given. Theoretical analysis and simulation results show that the DFH code generator which combines G with PN sequence increases security of DFH system without decreasing the SER performance.