To solve the problems that the narrowband radar range is low in resolution and is hard to separate trajectory group targets from range dimension, a method of separating group target signal components by using Discrete Sinusoidal Frequency Modulation Transform (DSFMT) is proposed. The modulation characteristics of micromotion ballistic target echo are studied and an echo model of micromotion signal is established. The energy aggregation characteristics of DSFMT are used to project multicomponent signal into transform domain. The objective function of parameter estimation is constructed to process the peak feature points in the transform domain, and the signal components are separated step by step. The effectiveness and robustness of the algorithm are verified.