Abstract: Abstract: The tractor equipped with steel belt power split CVT (continuously variable transmission) has multiple work sections, and it is easy to generate impact or even cause power interruption when shifting under load, which is an urgent problem to be solved in the development of this type of transmission. There are few studies in this field at present. In order to reveal the influence laws and mechanism of various factors on shift quality of tractor equipped with steel belt power split CVT, the shift process was simulated and a map representation method reflecting the overall trend of shift quality affected by 2 related factors (engine speed and load, terminational pressure and limited flow, shift starting time and shift timing sequence, tractor moment of inertia and tractor mass) was proposed. First of all, the transmission principle and the performance characteristics of the tractor equipped with steel belt power split CVT were described, including the speed regulation principle of the steel belt power split CVT, the tractive characteristics of the tractor, the maximum output power of the PTO and the fuel economy of the transmission. Secondly, the dynamic model about shift hydraulic system of the steel belt power split CVT was constructed and confirmed by 8 groups test under different terminational pressure, limited flow and shift timing sequence. Based on this, the tractor dynamic model including engine, steel belt power split CVT and rear axle was built. Finally, 3 evaluation indexes of shift quality, namely peak acceleration of tractor, dynamic load coefficient of transmission output shaft and sliding-friction work of clutch, were given. And the simulation about the influence laws and mechanism of various factors on shift quality was carried out. The results showed that the steel belt power split CVT not only could achieve sufficient power output, but also was more economical than the traditional transmission. The system fuel consumption of the steel belt power split CVT was about 20 g/(kW·h) lower than that of the traditional steel belt CVT under the same working condition. Lower engine speed (1 200 r/min), medium terminational pressure (5 MPa), higher limited flow (10 L/min), shifting before ideal shift point (0.2 s) and shift in overlapping sequence (0.2 s) all could improve the shift quality. However, the influence of transmission output shaft moment of inertia, tractor mass, as well as load on shift quality is complex, evaluation of each index on shift quality is not uniform, which needs to be synthetically considered at tractor design stage. According to the study, it is concluded that the steel belt power split CVT not only has high fuel economy, but also has simple shift laws and good controllability of shift quality, which has a good application prospect in medium and small power tractors. The research can provide theoretical support for transmission system design of the steel belt power split CVT.