As a typical hard and brittle material, gallium oxide crystal (β-Ga2O3) is easy to crack during processing. Diamond wire saw is the main way to produce β-Ga2O3 wafers. During the slicing process, a microcrack damage layer will be generated on the surface of the wafer. Under the stress, the microcracks will expand, leading to material breakage and fracture. In this paper, a finite element model of diamond wire sawing of β-Ga2O3 (010) crystal surface was established. The distribution of mechanical stress, thermal stress, and thermal-mechanical coupling stress during the sawing process were studied. The effects of sawing wire speed, feed speed and different parameter combinations under constant speed ratio on the thermal-mechanical coupling stress were analyzed. The research results show that: the thermal stress generated by sawing heat dominates the thermal-mechanical coupling stress during the sawing process; the mechanical stress caused by sawing force has a small numerical value and proportion, but it affects the distribution of thermal-mechanical coupling stress; increasing sawing wire speed and feed speed will increase the thermal-mechanical coupling stress.