Using micro tremors noise data recorded by the Yunnan Digital Seismic Network in 2016, we analyzed the site response of 47 seismic stations in 0.1~20Hz frequency band, based on the H/V spectral ratio method. We analyzed the single magnitude deviation recorded from earthquakes of M_L ≥ 2.5 in the Yunnan Digital Seismic Network from 2012 to 2016. The stations with single magnitude greater than the average magnitude of network are selected, and their single magnitude deviation are recalculated. The results show that all stations of the Yunnan Digital Seismic Network have a degree of site amplification because of many factors, such as the situation of site platform and geological structure. For most seismic stations, the excellent site response frequency is 1~6Hz, and the amplification is 2~4 times. Due to the effect of the site amplification, the single M_L magnitudes of 19 stations such as Dayao and Mangshi are greater than the average magnitude of the network. The deviations between the single magnitude and the average magnitude of the network are decreased, after the removal of the site amplification.