Using the ATG-6138m ercury detector recently developed by the Hangzhou Aadtech Co. Ltd.，a record of the co-seismic effect of mercury(Hg)vapor accompanying the 2015 Nepal MS8.1 earthquake was obtained in the Mile monitoring well，Yunnan Province. This is the first record of co-seismic effect obtained by mercury vapor observation in China. Such a fact implies that it would be possible to record more information about crustal dynamic effects，such as solid tide，co-seismic effect，etc.，by further improving the observation instrument precision and increasing the sampling frequency of the chemical quantity of subsurface fluids. This may help us to raise the capability of earthquake precursor monitoring and forecasting in the future.