For the purpose of studying the effect of the thermal-fluid-solid coupling on the fatigue life of T-pipe, the evolution of the pressure and velocity fields in the flow domain of the pipe was studied based on ANSYS finite element software, and the results were correlated according to the correlation theory and the Pearson correlation coefficient. The results show that the variation of the pressure and velocity in the flow field area has very little relationship with the temperature difference of the main branch pipe, and is closely related to the velocity difference of the main branch pipe. The variation of stresses in the pipe under complex stresses in the flow field and different initial stresses is obtained through the fluid-solid coupling analysis, and it is found that the maximum equivalent stresses in the pipe occur near the T-joint and the fixed end. On the basis of the Pearson correlation coefficient, the maximum equivalent stresses of the pipe and the fatigue life at the danger point were found to be significantly related to the temperature difference between the main branch pipe.