The work aims to study the effect of flexible rods on the dynamic performance of the box opener and the opening angle of the box with the increase of the working speed starting from the actual working conditions. SolidWorks was used to build the 3D solid model of the box opener. The pure rigid body model of the box opener was built by importing ADAMS, and the rod parts were flexibly processed by Ansys to generate the modal neutral file, which was then imported into the pure rigid body model to establish the rigid-flexible coupling model of the box opener for the dynamic simulation analysis. After the simulation, the load file was imported into Ansys for stress analysis of key components. The maximum corner of open box rod relative to suction box rod and the stress of the key components were obtained. It was concluded that the working speed 340 r/min was the limit speed of the box opening machine. By strengthening the strength of the rod parts, the box opener could run at a higher speed, but it was necessary to carry out comprehensive dynamic performance research and optimization. The rigid-flexible coupling analysis method can be used to more realistically simulate the actual motion state of the box opener, especially in the stage of a higher working speed; and compared with the pure rigid body model, it can analyze the dynamic performance of the box opener more comprehensively.