Abstract: This paper analyzes the detection performance of the coherent line-spectrum detector when the input data is real and windowed. Starting with spectral leakage, the method proposed in this paper effectively reduces the sidelobe level of leakage and hence improves the detection performance of weak real signals through windowing. Phase difference between segments of data at the same frequency is correspondingly compensated, which results in the coherent integration of data. Considering the situation of windowing and real-data, theoretical analysis and simulation show that the Window Phase-Compensated Processor (WPCPR) of this paper can 101gL (L is the number of segments) more signal-to-noise ratio (SNR) when compared with the Average Power Processor (AVGPR), thus widening the scope of coherent line-spectrum detection. Furthermore, this paper gives a physical interpretation of the new method from the perspective of frequency domain beamforming and points out the reason why the SNR improvement is not good as predicted.