The work aims to design an intermittent mechanism based on the combination of the connecting rod slotted offset crank-slider and the double-slider for the bag-supporting structure in the bagging device used after the formation of silage block in fodder machine, so as to realize the bag-supporting function of stopping and emergency returning, thus improving work efficiency. The artificial bag-supporting process was analyzed to design the bag-supporting mechanism and deduce the mathematical relationship between the stop time of the mechanism and the length of the connecting rod slot. Then, the rod length parameters of the offset crank-slider were optimized by Matlab, and Solidworks was used to establish model to simulate the operation of the bag-supporting mechanism. Finally, the rod length parameters and movement characteristics of the bag-supporting mechanism under three different stroke speed ratio coefficients were compared and analyzed. A set of relatively suitable parameters was selected from three sets of data to verify the formula, indicating that the bag-supporting mechanism had the function of stopping and emergency returning, and the simulation results were consistent with the calculation results of the analytical formula. The bag-supporting mechanism is reasonably designed, which meets the technological requirements, and provides a feasible solution for the automatic bagging of silage blocks.