The conventional vertical rape windrower, whose laying direction of the rape plants is perpendicular to the forward direction of the windrower, still has the challenge to guarantee stable feeding rate of the following pick-up operation due to the inconsistent laying angle, highlighting a need to change the way of laying. As a solution, a forward laying device for rape windrower, whose operation parameters were analyzed, was proposed and the simulation experiments was carried out to optimize the laying quality based on ADAMS. Focusing on the moving of the rape plant at the outlet of the header, the horizontal throwing movement of the plant and its following fixed axis rotation after landing at the ground were analyzed based on kinematics and dynamics, indicating that the laying angle was related to the initial velocity and fixed axis rotation time of the plant. It was found that the main factors affecting the laying quality were forward speed of the windrower, speed ratio of transverse conveyor chain, and inclination angle of the header. Furthermore, the laying process under the coordination of the wheel and the guide plate was analyzed. The number of wheel teeth was 7 while the rotational angular velocity was 6.27rad/s. In addition, the curve parameter equation of the guide plate was also determined, and a four-bar mechanism was designed. Based on ADAMS, a multi-body kinematic simulation model of the forward laying device was constructed. By taking the forward speed of the windrower, transverse transmission chain speed ratio and inclination angle of the header as factors, the laying angle was utilized to evaluate the laying quality in the Box-Behnken simulation experiment with three factors and three levels. The mathematical relationship model between the laying angle and every factor was obtained to figure out the optimization objective function to minimize the laying angle. With the assistance of the DesignExpert software, the optimal parameter combination was obtained, and then it was validated by simulation and field experiment. The results of the Box-Behnken experiment indicated that the optimal parameter combination was forward speed of 0.93m/s, transverse conveying chain speed ratio of 1.11, and inclination angle of 117.93°. The theoretical optimal laying angle was 15.25° under this condition. The results of the simulation experiment illustrated that the simulation value of laying angle was 14.42° under the optimal combination of parameters, and the relative error was 5.4% when compared with the theoretical value. The field experiment showed that the forward laying device could work smoothly without blockage. The average laying angle, average laying width and average laying height were 17.25°, 752mm and 323mm, respectively, which could meet the demand of actual production. The research could provide a reference for the structural improvement and optimization of the laying device for vertical rape windrower.