Traditional screw motors with rubber stators are difficult to adapt to the high temperature and high pressure conditions of ultra-deep wells. Aging, deformation, and carbonization of the rubber stator lead to motor failure. In order to develop a volumetric power drilling tool that can be used for drilling at a depth of 10 000 meters, a full-metal screw motor suitable for ultra-deep wells was designed. The deformation law of the motor under high temperature and high pressure was discussed by numerical simulation, and the deformation law of the motor under different factors was analyzed. The results show that within the research range, the maximum deformation of the metal stator and rotor is less than 0.25 mm and 0.16 mm respectively. With the increase of ambient temperature and drilling fluid dynamic pressure, the stress and deformation degree of the motor show an increasing trend. When the ambient temperature increases, the gap value of the motor will increase and the volumetric efficiency will decrease. Ambient temperature is the main factor affecting the deformation of the motor compared to pressure. Therefore, the design of metal motors needs to pay attention to the effects of temperature within a reasonable range.