In view of the difference between the torque distribution principle in the hybrid gearshift schedule calculation and the actual operation condition, on the basis of a parallel pulg-in hybrid electric vehicle (PHEV), the torque distribution principle was formulated with the velocity, throttle opening and battery SOC as control parameters. Considering the influence of dual power source synergy and battery SOC, the calculation principles and methods of dynamic and economic improved two-parameter gearshift schedules were defined, and the dynamic gearshift schedule was gained with maximizing traction as optimization objective, as the economic gearshift schedule was gained with maximizing systematic efficiency as optimization objective. The simulation of the proposed improved two-parameter dynamic and economic gearshift schedules were compared to the initial gearshift schedule on the platform of AVL Cruise and Matlab/Simulink. The acceleration time of 0~100 km·h^-1 is shortened by 5.9%, and the consumption of SOC balanced is reduced by 10.4% and 7.5% respectively under the NEDC and WLTC.