In order to explore the new seismic monitoring technology and method of underground fluid，fault gas concentrations of hydrogen have been carried out at the piedmont fault zone of Zhongtiao Mountain． Through the experiment of observation positions，gas collection devices and sampling depths，we proposed fault gas observation methods of online automatic trace hydrogen analyzer． The comparative tests were done on the stability and suitable conditions of the instrument in the field environment，and the hydrogen concentrations at different measuring points of the same fault were observed． The results showed that it is feasible to carry out hydrogen concentration observation in a fault zone continuously． We suggested that the method in this study could be a useful tool for setting observation points，choosing the reasonable observation depth and scientific analysis of the observed data．