Abstract: Small and scattered fields are found for the rapeseed production in the hilly and mountainous regions. It is still lacking on in the mechanized threshing and cleaning equipment for rapeseed. The large grain loss is also observed during the operation of small-sized threshing and cleaning equipment. This study aims to propose a rapeseed harvesting scheme in the hilly areas. The functions of the forced feeding can be integrated by fish-scale double pressure rolls. The threshing and separation can be combined with the rasp bars and spike teeth, and cyclone separation. The 5TYC-120A type rapeseed threshing machine was developed in the production area. The overall structure of the rapeseed threshing machine was determined using the kinematic and dynamic analysis. The parameter range of the forced feeding device was determined with the fish-scale double pressure rolls, in order to realize the adaptive clamping and conveying of the feeding quantity. The threshing and separation device was combined with the rasp bars and spike teeth. The cyclone separation cleaning device was determined for the key influencing parameters on the threshing and cleaning performance. Taking the rapeseed threshing machine in the production area as the test platform, single-factor tests were carried out to determine the influence of the rotational speed of the fish-scale double pressure rolls, the rotational speed of the threshing drum, the threshing gap, and the wind speed at the debris suction opening on the operation performance. The optimal ranges of the parameters were determined after the test. The rotational speed of the threshing drum, the threshing gap, and the wind speed at the debris suction opening were selected as the test factors. A three-factor and three-level quadratic orthogonal combination test was carried out with the loss rate and impurity content rate as the evaluation indexesindices. The regression models between the evaluation indexes and the test factors were constructed after multi-objective parameter optimization. The optimal combination of the operation parameters was determined as follows: The rotational speed of the threshing drum was 450 r/min, the threshing gap was 27.5 mm, and the wind speed at the debris suction opening was 15.76 m/s. The field verification test showed that the loss rate of threshing and cleaning was 4.78% under the optimal parameter combination, while the impurity content rate was 3.98%. This finding can also provide a strong reference to optimize the low-loss threshing and cleaning during rapeseed harvesting.