Active stealth of warship is an important developing direction in modern stealth technology field. Based on scattering properties of warship and characteristics of linear frequency modulated (LFM) signal and its matched filter, the cancellation signal was designed. Warship stealth was achieved through interference cancellation between cancellation signal and radar echo signal. Simulation results show that complete stealth of warship can be achieved through canceling LFM echo signal, and the scattering field of warship can be reduced by almost 10 dB even with some cancellation error. The proposed method can provide important reference for warship's active stealth in project realization.