Abstract: Before and after the 2008 Wenchuan Ms8.0 earthquake,emitting of mud appeared twice in Tanggu district of Tianjin and made tremendous social impact.On-site investigation carried out by experts of earthquake administration of Tianjin Municipality and concerned department shows that the gas company causes the phenomenon when they laid gas pipes adopting trenchless technology.In construction,they dug underground level drilling;the pressure of the mud is so large that the mud emitted from the weak part of the stratum.Therefore,the emitting of mud is not seismic precursor.The verification of the phenomenon greatly stabilizes the local people;soon after,the result was applied in the verification of mud emitting in Ninghe County on June 26th,2008.