Triangular rotor is a core component of small aviation Wankel rotary engine, subjected to complex load coupling effects such as temperature, inertial force and gas explosion pressure in the process of highspeed rotation, and more prone to failure and damage due to insufficient strength. In view of the stress concentration and strength evaluation of triangular rotor, a model of the engine's thermodynamic working process is established to obtain the change law of the cylinder temperature, cylinder pressure and heat transfer coefficient of the combustion chamber in a single cycle of the engine,and calculate the thermal boundary conditions everywhere in the rotor.Under conditions of mechanical stress, thermal stress and thermomechanical coupling, the finite element method is adopted respectively to simulate and analyze the temperature field, stress field and deformation of the triangular rotor. And optimization methods such as the processing of rounded corners at the edge of the round hole at the waist of the rotor and the arrangement of heat sinks at the cooling hole are proposed, and comparative analysis is carried out.The simulation results show that after the optimization, the stress at the edge of the circular hole at the waist of the rotor is reduced to 403.9 MPa from 687.0 MPa, which is about 58.7% of the original, and the stress value at the cooling hole is also reduced to 113.2 MPa from 202.6 MPa, which is 55.9% of the original. Cooling fins being arranged, a drop of rotor at temperature is more than 20 K on average, the temperature of the round hole at the waist of the rotor and the cooling hole dropped is about 40 K, and the deformation of the sealing groove tip is reduced to 0.15 mm, from 0.21 mm, i.e. a reduction of 27.7%.