Taking the fourth-stage transmission system of the konjac flour machine as the research object, a multi-body dynamic model was established based on the straight tooth synchronous belt and double helical synchronous belt with new profile, and the influence of the tooth line shape on the belt tooth stress and system vibration was analyzed. Then the influence of the structural parameters of the helix angle and the dislocation coefficient between the teeth on the dynamic performance of the transmission system were investigated. The results showed that when the toothed helix angle β was 30° with the inter-tooth dislocation coefficient k of 0.00, the tooth root stress of the belt tooth was smaller. Under this condition, the stress distribution was more uniform, and the lateral vibration was smaller, with lower transmission error and smaller interference fluctuation.