In the Yangtze River Estuary water area,the combination of the traditional tide and GPS-RTK water depth measurement method is used widely.But the existing tide level stations are unable to control the whole area,and RTK differential signal which cannot cover completely is restricted by distance.The precision of water depth measurement is low.The GPS-PPK technique has much superiority such as wider operating range,faster measurement speed,and higher positioning precision.It is not limited by radio transmission distance and communication network environment.Based on the accuracy test of different operating distance,the GPS-PPK technique has higher operational efficiency and accuracy than the combination of the traditional tide and GPS-RTK method.The new technique can be applied to the water depth measurement in the Yangtze River Estuary.