GPS RTK（real-time kinematic ） survey is affected by the satellite signals and transmission of RTK radio stations，the mobile station cannot obtain the fixed solution. For solving this problem，the working principle，field operations，and data processing methods of GPS PPK （post-processed kinematic）are studied. In the survey of Yushan marine，the method of known point check and elevation comparison between the RTK inspection line and the PPK main survey line is used to statistically analyze its measurement accuracy. The results show that when the application of RTK is limited，the survey accuracy of PPK is consistent with that of RTK.The combined application of PPK and RTK can improve operational efficiency and data reliability，which not only saves the survey costs but also shortens the construction period，therefore PPK technology is worthy of promotion in the marine survey.