Abstract: The data quality of GNSS buoy working in the sea is ususlly influenced by the dynamic sea surface, The measurement noise and multipath error are significantly increased, and cycle occurs more frequently, especially when the satellite is at low elevation. The conventional GNSS cycle slip detection method always neglect the effects of multipath error and observation noises and take no account of error caused by satellite elevation when detecting and repair the the GNSS data. Thus, the conventional GNSS cycle slip detection method is not applicable for GNSS buoy. In this paper, the author proposed a combined cycle-slip detection method based on TECR and an improved M-W measurement that taking into account the satellite elevation angle.The experiment results indicate that the method can significantly reduce error caused by satellite elevation and multipath and can accurately detect and repair all the simulated cycle slips. Thus,It’s an effective method for data preprocessing applied to marine GNSS buoys.