Using the 116 earthquakes with ML ≥ 3.8 in the Inner Mongolia region from 2008 to 2015,we remeasured the near earthquake magnitude ML and surface wave magnitude MS,based on 1 norm linear regression(SR1 and SR2)and 2 norm(OR)orthogonal regression method. We established the conversion relationship between ML and MS. The result was tested with the Gaussian disturbance. The result shows that the orthogonal regression method(OR)result has the best fitting curve,and the conversion relation is MS=0.96 ML-0.10. The difference between our result and Guo Lvcan's(MS=1.13 ML-1.08)may be caused by regional tectonic characteristics. Inner Mongolia MS value is significantly higher than MS experience value,with the average difference of 0.23,the difference distribution of experience relation and the rectified relation is in the range of 0.2~0.3.