Abstract: Wave is one of the important and complex oceanographic hydrological elements. It is, therefore, of great significance to conduct stable, long-term and effective monitoring of sea waves. In view of the problem that traditional wave observation equipment is expensive and poor in real-time performance, a drifting buoy real-time online wave measurement technology and its implementation method are studied, which is based on the carrier phase epoch differential algorithm of the Global Navigation Satellite System (GNSS) and include mainly the hardware selection and composition and the design ideas and working principle of the real-time online software. By comparing and analyzing the real-time wave measurements returned from the offshore and open sea trials, the real-time online wave measurement technology of GNSS drifting buoy and the feasibility and accuracy of its software are validated. During the tests in the offshore area, the results measured and returned real-time by 2 sets of the GNSS test buoys are compared with those exported from the Datawell DWR-G4 buoy, showing that the root mean square (RMS) of the significant wave height differences resulted from the two buoy systems is 6 cm and 4 cm, respectively, being better than the technical index (0.1 m + 5%H, H is wave height) of the mainstream wave measurement buoys. The RMS of the mean wave period difference measured with the two buoy systems is 0.48 s and 0.49 s respectively, indicating that the results transmitted real-time have good retrieval performance. In the open sea tests, the significant wave height and the mean wave period returned real-time by four test buoys are highly consistent with those of the reanalyzed products.