With the advancement of the rice cultivation technology and the vigorously promotion of the super hybrid rice, the rice yield is increased rapidly, which proposes higher demand for the performance of the threshing and separating device for the largeamount feeding combine harvester (7~9kg/s feeding amount). When facing large feeding amount, the transition between tangential flow roller and longitudinalaxial flow separating roller will easily get blocking. In order to optimize the structure of newstyle threshing and separating device in oblique tangentiallongitudinal combine and to meet the requirements of highyielding rice harvest at present in China, rice harvest in field was conducted to study the influence of speeds of tangential drum and longitudinal drum, structure form of the tangential drum concave, gap of the conical spiral transition and cover on the performance of total consumption and total loss. The combine was reconstructed based on selfdeveloped oblique tangentiallongitudinal combine and load test system was built for the combine. Orthogonal test with three factors and three levels was carried out in the combine. Optimal parameters were gained by orthogonal test range analysis method. According to the analyzed results of orthogonal test, the rotational speeds of tangential drum and longitudinal drum were 862r/min and 806r/min. The structure form of the tangential drum concave was the type of orientation and separation hole. The gap of the conical spiral transition and cover was 50mm. Under the optimal parameters, the field experiment results were total loss rate of 062% and total power consumption of 40.42kW.