Low temperature high-speed motors can achieve low temperature and high viscosity fluid media efficient transmission, meanwhile, excessive friction loss and temperature rise issues are addressed. In this paper, a 30kw low-temperature and high-speed permanent magnet motor prototype is implemented as the research object. Three stator axial cooling structures are proposed to effectively control the motor temperature rise. First, the discussion focuses on the friction loss in the air gap and its related influencing factors; at the same time, the effect of different axial cooling structures on the friction loss in the air gap is also considered. Secondly, a calculation method of axial viscous friction loss based on the principle of fluid force equilibrium is proposed in the paper, the variation law of the structure size influence on axial friction loss is also given. Based on the quantitative calculation of axial friction loss, the final structure size is determined by synthesizing the variation of different size structures stator iron loss. Finally, the physical model of the three-dimensional fluid-thermal coupling calculation on the analysis object is established by means of finite element analysis, and the stator temperature rise distribution is calculated.