Significant Wave Height (SWH) is one of the major elements widely used to describe ocean waves as it correlates well with visually estimated heights. In this study, we applied GNSS Interferometric Reflectometry (GNSS-IR) technique to measure the SWH. We introduced Confidence Level of Retrieval (CLR), which demonstrates the coherence of the interference generated by the reflected signal from the surface of ocean. In order to validate our approach, we installed GNSS equipment in Duck, North Carolina and collected GNSS observations during 4 - 31 December, 2020. The time series of the CRL were compared with the SWH observed from a nearby wave buoy. Overall, the CLR shows a good agreement with the buoy data with the correlation coefficient (CC) of 0.81. In particular, the CC improved to 0.88 when the wave heights were lower than 1.5m. The experimental results show that the proposed approach is feasible to monitor the SWH that is a promising complementary tool for SWH measurements.