In order to study the flow characteristics of an integrated natural circulation reactor under inclined conditions, a typical three-dimensional analysis model of natural circulation was established. The natural circulation under inclined conditions was numerically simulated using the computational fluid dynamics method, and the velocity and temperature distribution characteristics of heat exchangers and mixed-flow channels with different inclined angles were analyzed. The results show that as the inclination angle of the heat exchanger flow rate increases, there is a spatial migration phenomenon corresponding to the direction of the average flow rate. A large inclination angle will lead to a serious deterioration of the natural circulation capacity in the lower channel. Under inclined conditions, there is a phenomenon of temperature stratification in the mixed-flow channel.