The work aims to improve the packaging efficiency of the lentinus edodes packaging machine and improve the overall performance of the packaging machine. First, basic parameters, stretching characteristics and manual packaging methods of the packaging bag were analyzed and studied. The design scheme of the round supporting device was obtained by analogy with manual packaging. Based on this scheme, the key structural dimension parameters of the round supporting device were designed in detail. The 3D model was established and imported into ANSYS for static analysis to get the force distribution pattern. The results showed that the maximum pressure stress of the round supporting mechanism during action was 2.48 MPa, which was much smaller than the bending strength of resin 67 MPa. The maximum strain was 0.175 mm, which happened at the front end of the round supporting mechanism. It did not affect the post sequence action. The design rationality of the round supporting device and the accuracy of model established are proved. It provides a certain theoretical reference for design of similar structures.