A method for mitigating a leakage signal in an FMCW radar and a radar system thereof are disclosed. The method for mitigating the leakage signal in the radar system includes generating an in-phase signal and a quadrature signal for a beat signal, generating a complex signal using the in-phase signal and the quadrature signal, concentrating a phase noise of the leakage signal included in the complex signal on a stationary point, and mitigating the phase noise based on stationary point concentration (SPC) of the phase noise.