Because its capability in long-range imaging with simple hardware architecture, the stepped frequency modulated signal has an obvious advantage in modern radar target recognition. The principle of synthesizing the range profile using stepped frequency modulated signal is derived. However, the radar echo is sensitive to target motion, which makes the range profile blurred. To solve this problem, a novel type of stepped frequency modulated signal is put forward, in which the pulse repetition time is variational. The target velocity-frequency coupling is avoided by predesigning the pulse repetition time, and the influence of acceleration is eliminated by phase cancellation. The precision request of the pulse repetition time is discussed. Simulations with synthetic data confirm the effectiveness of the proposed method.