Abstract: A phase-analysis based Capon-amplitude phase estimation of a sinusoid (CAPES) method is proposed for parameter estimation of single frequency signal. The proposed method uses the phase difference between two data segments to reduce frequency estimation error caused by the picket fence effect and therefore to improve the estimation accuracy of frequency, amplitude and phase. Computer simulation indicates the new method can achieve better parameter estimation performance than that of the traditional CAPES method. We applied the proposed method to experimental data collected by a trail over-the-horizon radar (OTHR) and the results validates the effectiveness of the proposed method.