Abstract: To analyze the effect of peripheral-ported shape on the performance in a hydrogen/gasoline bi-fuel rotary engine, a CFD model was implemented and validated by the experimental data. The flow field, combustion process and major emissions formation in rotary engines with different peripheral-ported shapes were numerically studied. Results show that the mixture in the cylinder was squeezed and the backflow phenomenon occurred during the end of the intake stroke. The larger the corresponding peripheral-ported area was, the more evident the backflow phenomenon of the mixture would be. At the end stage of compression stroke, a mainstream flow field whose direction was identical to the rotor rotating direction was formed. The shape of peripheral-ported had little effect on the velocity of the mixture in the cylinder at ignition timing. Compared with the round shape, as the peripheral-ported shape was triangle, the average turbulence kinetic energy and peak pressure increased by 26.91% and 5.87%, respectively, and nitric oxides emissions increased due to higher in-cylinder temperature.