Abstract: Abstract: When the tractor assembled with dual-clutch automatic transmission shifts under the condition of working with heavy load in the field, the original shifting quality evaluation indices can't fully investigate their impacts on the performance, so 2 evaluation indices, which are transfer coefficient of transmission's output torque and transmission's output torque, are proposed. The transfer coefficient of transmission's output torque is used to evaluate dynamic load which is produced in shifting process of the tractor assembled with dual-clutch automatic transmission; and the transmission's output torque is used to evaluate power in shifting process of the tractor assembled with dual-clutch automatic transmission. The pattern has been concluded that the superposition degree of 2 groups of clutches (one group is connected with odd gear input shaft, and the other is connected with even gear input shaft) has an effect on shifting quality. In the shifting process of the tractor with dual-clutch automatic transmission, in order to ensure ride comfort, power performance and durability of the transmission system, 2 groups of the clutches should have appropriate superposition in the separation and combination processes. If the superposition degree of 2 groups of clutches is insufficient, it could cause transfer coefficient of transmission's output torque and transmission output torque to decrease and even make power performance and durability of the transmission system enter a poor condition; if the superposition degree of 2 groups of clutches is excessive, it could cause jerk degree and sliding-friction work to increase, even make ride comfort enter a poor condition and shorten the service life of clutch. The dynamic equations of the shifting process of the tractor assembled with dual-clutch automatic transmission have been built and the shifting process has been analyzed. The shifting process is divided into 5 stages. The change trend of the speed and torque of the clutch and engine in each stage is analyzed. Based on the Matlab/Simulink/Stateflow software platform, the simulation model of the whole shifting process has been built. Dongfanghong-1804 tractor is selected as the reference object, and its shifting process has been simulated in plowing conditions. Relevant simulation results indicate that when the lag time of clutch's oil pressure rising is 0, 0.1 and 0.2 s, the corresponding minimum transfer coefficients of transmission's output torque are 0.42, 0.36 and 0.12, respectively, and the corresponding minimum torques output by transmission are 2 257, 1 932 and 725 N·m, respectively. According to the analysis of simulation data, as the lag time of clutch's oil pressure rising extends, the decline degree of transfer coefficient of transmission's output torque becomes larger to cause dynamic load to increase gradually, and the transmission's output torque becomes smaller to make tractor's power performance worse. The 2 new shifting quality evaluation indices can fully evaluate tractor dynamic and dynamic load which is generated in the process of shifting; they are good compliments to original shifting quality evaluation indices and improve the shifting quality evaluation system of the tractor assembled with dual-clutch automatic transmission. Above all, the results of this paper provide some theoretical basis for formulating shifting control strategy of the tractor with dual-clutch automatic transmission.