In order to observe the three-phase boundary (TPB) variation of the porous gas electrode, a new laying style of the porous gas electrode was proposed. Two electrodes with different ingredient were taken in the experiment under the same condition to testify that there are three distinct stages of the TPB dynamic variation.Each stage has its own apparent phenomenon and the variation time of each stage is different for each electrode. The relationship between the electric conductance and the TPB variation of the electrode were also analyzed by the theoretical calculating formula. The result showed that the internal resistance increases as the decrease of the electric conductance created by the TPB variation. The research above illustrated this laying style of the porous gas electrode can be effectively used to observe the TPB dynamic variation.