Abstract: In order to improve the operation quality of vertical rape windrower, the effects of rape plant characteristics and windrower parameters on laying angle were studied in this study. The structure and working principle of the vertical rape mower were described. The laying process of rape plant was divided into falling process and rotation process according to the working principle of the rape windrower. The movement state of rape plant during the laying process was analyzed based on the dynamic theory, and the mathematical model of laying angle was established and the influencing factors were analyzed. Analysis results showed that the laying angle influenced by material parameters of rape plant and working parameters of windrower. ANSYS and ProE software were used to establish the flexible body of rape plant and windrower model, respectively. Then the rigid flexible coupling model of windrower and rape plant was established in ADAMS software, and the single factor and multifactor simulation experiments of laying process were carried out. The results of single factor experiments showed that with the increasing of the plant height in the range of 1.2-1.6 m, laying angle decreased and reached the minimum value at the plant height of 1.4m, and then increased. The laying angle increased and then decreased when the plant mass density was in the range of 438-588 kg/m3, and reached the maximum value at the plant mass density of 538 kg/m3. When the friction coefficient between plants increased in the range of 0.1-0.5, the laying angle decreased. The results of multifactor experiments showed that forward speed, speed ratio and the interaction between forward speed and stubble height had a significant influence on laying angle (P < 0.01).The significant order of factors was speed ratio, forward speed and stubble height. The quadratic regression equation model was established according to the results of multifactor experiments, and the response surface methodology was utilized to analyze the influence of interaction on the laying angle. Optimization equations and constraints were established, and optimal parameters of windrower were determined that forward speed was 0.6 m/s, the speed ratio was 1.37, and stubble height was 0.42 m. The field experiments were carried out and the results indicated that the relative errors between predicted and measured values of laying angle were less than 6%。Compared with the control tests, the laying angle of rape plant decreased from 134.9° to 115.8°, the angle difference decreased from 11.2°to 9.6°, the root difference decreased from 0.22 m to 0.14 m, and the loss rate decreased from 2.2% to 1.5%, the working performance of rape windrower improved. The research results can provide the basis for determining the suitable conditions of rape cutting and optimizing the operation parameters of the windrower.