Frequency-agile radar has the advantage of strong anti-jamming capabilities, but frequency agility causes coupling between target range, velocity, and carrier frequency in the echo phase, which affects coherent accumulation. Most existing methods involve high computational complexity, making them difficult to apply on platforms with limited computational resources. This letter proposes a fast HRRP generation method that does not require velocity phase compensation to generate HRRP. This method uses a specially designed waveform to convert the velocity-related phase in the echo into a linear phase. Based on this, conjugate multiplication of the echoes is performed to further transform the linear velocity term into a constant phase, and HRRP is generated using FFT. Simulation results show that this method ensures imaging quality while also offering high computational efficiency, providing a feasible solution for fast imaging in frequency-agile radar.