Abstract: Abstract: A combined windrower has widely been used for oilseed rape harvest in recent years. However, there is a limit laying space in the small windrower with a narrow swath. The side transmission is also difficult as a result of the tangled and lodged rape, particularly in the branch involvement overhead during cutting and conveying. In this study, a feasible mechanism of inclined transportation was proposed for the large-branch involvement in the oilseed rape, thereby a novel device of inclined transportation was designed for a rape windrower. An inclined windrower table was used for the large laying space of the rape stalk, thereby improving the transport capacity along the transverse direction. A systematic analysis was made on the process of cutting, transporting, and laying stalk in the inclined transportation of a rape windrower, according to the geometrical and kinematic conditions of the stem in the smooth migration. As such, the structural and performance parameters were determined, including the reel speed, conveyor belt speed, and conveyor angle. A field test was conducted to evaluate the laying quality of inclined transportation in a rape windrower. An optimization was made on the structural parameters of working parts to establish the constraint equations of operating parameters for the inclined transportation windrower. A quadratic regression orthogonal experiment was carried out to explore the interaction factors on the laying quality. The evaluation indices included the laying angle, the laying angle difference between the upper and lower floor, as well as the variation coefficient of laying width and height. The ranges of experimental factors were obtained, where the rotate speed of the reel was 26-38 r/min, the linear velocity of the conveyor was 1.4-1.8 m/s, and the conveyor angle was 10°-30°. Quadratic multivariate fitting regression and variance analysis were applied to clarify the influence of interaction factors on the performance of inclined transportation windrower. Results showed that the conveyor angle had the most significant influence on the laying quality. A multi-objective optimization model was established after the quadratic regression orthogonal experiment, according to the standard requirements of the rape windrower. An optimum combination of parameters was achieved, including the reel speed of 35 r/min, conveyor belt speed of 1.5 m/s, and conveyor angle of 27°. In the field test, the results showed that the average spread angle was 28.3°, and the relative error with the predicted value was 5.6%, under the optimal combination of parameters. The laying angle difference between the upper and lower laying floor was 5.4°, where the relative error with the predicted value was 12.5%. The variation coefficient of laying width was 9.6% with a relative error of 15.6%, while, the variation coefficient of laying height was 8.6% with a relative error of 11.7%. The accuracy of laying quality in the prediction model was verified by the field test. The swathing loss rate and operating efficiency were 0.73% and 1.11 hm2/h, respectively. The water contents of rape stem and grain were 47.9% and 9.7% after 4-day drying, which decreased by 35.1% and 74.4%, respectively, compared with those before, indicating a great benefit for the following picking and threshing. Compatibility tests of inclined transportation windrower were carried out in the winter rape areas, including the upper middle and lower reaches of the Yangtze River, as well as the spring rape area of North China. The results demonstrated that the inclined transportation windrower can realize smooth transportation, neat laying, high quality, and low loss swathing, suitable for the multi-cropping rape in two-stage harvesting. This finding can provide a sound reference to design and optimize the rape windrower. A further dynamic characteristic of rape stalk during transport and laying is necessary for the better performance of inclined transportation in the future.