Experimental data of Ag/La2NiO4 base electrical contacts in the condition of DC 18V/30A were obtained by electrical contact experimental instrument. The morphology of anode and cathode surface, arc erosion and weight change were analysis. A transient temperature field model of electrical contacts was established by the following procedure analysis: the close arc→ the contact resistance Joule heat → the open arc. The features and distribution of the transient temperature field were calculated by finite element method according to the experimental data. From the results, not only the feature of arc erosion and direction of mass change were predicted, but also the important information about material melting and vaporization were understood, which are valuable to research the erosion mechanism and lifetime for the Ag/La2NiO4 base electrical contacts material.