Differential frequency hopping (DFH) is a kind of new frequency hopping (FH) technique. Based on the encryption principle of affine cipher, a frequency transition function of DFH is designed. This function is convenient for realization, easy in controlling the secret keys and also has more secret keys. The final results of experiment prove that the frequency hopping pattern based on this function is good in uniformity, so the system has high complexity and strong anti-attack features.