Precise monitoring of tide variation is the most of issues in the fields of Global Sea-level Observation System,ocean circulation and global climate change research. With the deepening research and rapid application of GNSS,GNSS-MR based on multipath has gradually become a new means of remote sensing for ground environment (vegetation,soil moisture,snow depth,sea level,volcano and so on) with geodetic GNSS station. By analyzing the characteristics of the onshore GNSS SNR data which is caused by multipath,the inversion principle of GNSSMR technology based on the SNR data to detect tide variation is given in this paper. The onshore GNSS station of SC02 which is located in Friday Harbor,Washington state of United States,are used to retrieve tide variation. The retrieval result is consistent with the tide gauge which is only 359 m to the GNSS station. The bias is about 10 cm, and the correlation coefficient is better than 0.98. Preliminary results show that GNSS-MR technology based on onshore CORS station to some extent could be real-time and continuously used to monitor the tide variation. What' s more,onshore GNSS stations could be a powerful supplement for tide gauge and be used to extend GNSS application in marine remote sensing field.