GNSS PPK(post processing kinematic)is a dynamic post-processing technology which is free from the restrictions of radio transmission distance,and the distance can reach 80 km.In order to solve the problem of the bathymetric survey in the coast long channel,we propose the method of GNSS PPK 3D bathymetric survey,which improves the accuracy of the bathymetric survey without tide extraction and tide fitting,and avoids the cumbersome secondary development using the existing commercial software TBC and Hypack.The principle of the GNSS PPK positioning and GNSS PPK 3D bathymetric survey is introduced,and the implementation method of GNSS PPK 3D bathymetric survey based on Hypack 2014 is expounded.It is valuable in the bathymetric survey of the coast long channel.