In order to analyze the influence of degree of hybridization and the number of electric motors on the climb performance of small series architecture universal hybrid-electric aircraft and the selection of different performance parameters in the climb stage, according to the aerodynamic model of the hybrid-electric aircraft and the system model of tandem structure, the degree of hybridization, the climb speed, the angle of climb, the number of electric motors and the take-off mass were taken as the optimization variables, and the amount of fuel for the climb and the extra payload were taken as the objective functions, and the optimization model of the climb performance of the hybrid-electric aircraft was established. Multi-objective particle swarm algorithm(MOPSO) was used for optimization solution. Taking the small series architecture universal hybrid-electric aircraft as an example, the performance parameters are derived and compared and analyzed. The optimization results show that the multi-objective particle swarm algorithm has a good optimization effect on reducing the amount of climb fuel and increasing the extra payload. When the degree of hybridization is 0.99, the climb speed is 51 m/s, the climb angle is 7°, the number of electric motors is 1 ~ 4, the take-off mass is between 1 730 ~ 2 200 kg, the climb fuel consumption is minimum and the extra payload is maximum.