Aiming at the problems of large thermal resistance and uneven light output of high-power vertical cavity surface emitting laser (VCSEL) array,this paper studies the action mechanism of ohmic contact resistance of p-GaAs layer and the method of reducing ohmic contact series resistance,so as to improve the uniformity of light output power of VCSEL array.Based on three commonly used ohmic contact metals Ti/Au, Ni/Au and Ti/Al /Ti/Au,the effects of metal thickness and metal combination on p-type ohmic contact resistance are studied.Combined with plasma surface treatment process,the inerface state of metal/p-GaAs is improved, the effect of metal/p-GaAs interface state on ohmic contact resistance is studied.The experimental comparative analysis shows that the specific contact resistivity of ohmic contact of metal Ti/Au structure electrode is the lowest,which is 3.25×10-4 Ω·cm².Based on the metal/semiconductor contact potential barrier model,the interface potential barrier can be reduced by 12.6% (0.269 2 eV to 0.235 3 eV) by surface plasma treatment,and the plasma bombardment power can regulate the potential barrier and density of states on the metal/semiconductor interface.