In order to obtain the optimal structure and operational parameters of the threshing and separation device of tangential-longitudinal combine, rice harvest in field was conducted to study influence of tangential drum-concave gap, longitudinal drum-concave gap and speed of tangential drum and longitudinal drum on the performance of total threshing-and-separation power consumption, tangential drum power consumption, longitudinal drum power consumption and entrained loss. The combine was re-constructed- based on self-developed tangential-longitudinal combine and load test system was built for the combine. Optimal parameters are gained by quadric polynomial regress analysis and complex method, and tangential drum-concave gap is 30.99mm, longitudinal drum-concave gap is 14mm and the speed of tangential drum and longitudinal drum is 892.95r/min and 848.95r/min respectively. The test result showed that on the parameter’s condition, total power consumption was 39.03kW, power consumption of tangential drum and longitudinal drum were 11.72kW and 27.31kW respectively and the entrained loss rate was 0.50%. Mixture distribution under tangential drum and longitudinal drum was analyzed, and it provide basis for design and optimization of cleaning unit.