In order to study the flow and heat transfer process of the fluid in oblique tee, the CFD simulation of flow and heat transfer processes of the fluid in oblique tee with the included angle of 20o-90o, the velocity ratio of 2-3.5 and the branch position of 500mm-1000mm were carried out based on Fluent software, and the sensitivity analysis of various parameters influencing the average heat transfer coefficient of wall surface was conducted by orthogonal experimental design. The results show that as the included angle or velocity ratio increases, the maximum velocity of fluid at the outlet of oblique tee increases gradually, and the influence of velocity ratio is more significant. The average heat transfer coefficient of wall surface also increases with the increases of included angle and velocity ratio, but the decrease of branch position; the branch position mainly affects the average heat transfer coefficient of wall surface, and its influence on the velocity is negligible. The average heat transfer coefficient of wall surface is increasing with the decrease of the branch position. According to the different effects of various parameters on average heat transfer coefficient of wall surface, branch position l > velocity ratio λ >included angle θ, which means that the closer the branch pipe is to the inlet of main pipe, the greater the velocity ratio, and the greater the included angle, the better the heat transfer effect of wall surface will be. Therefore, the branch position is the primary factor to influence the heat transfer effect of oblique tee.