Seismic station records of M ≥4. 0 earthquakes in the Yunnan Regional Digital Networks in 2000 ～ 2011 were used to determine near earthquake magnitude ML and wave magnitude MS of 433 earthquake waveform data． The speed data were simulated: near earthquake magnitude ML was simulated in terms of short cycle seismographs by DD-1 records，and surface wave magnitude MS in terms of the long cycle seismographs by SK records． All the ML and MS data were then man-checked with linear regression and orthogonal regression and obtain the conversion formula between them． Results showed that the formula MS = 1. 13ML － 1. 08 used since the 1970s may cause problems when applied to the Yunnan region． The adjusted formula of MS = 1. 13ML － 0. 86 is more applicable as the new conversion relationship． Meanwhile，the comparison between the recorded data from Yunnan seismic network and the national seismic network shows the ML difference of － 0. 2 ～ 0. 4 in most of these data with 0. 2 as the majority and MS difference between － 0. 4 ～ 0. 2 with － 0. 2 as the majority．