The work aims to improve the accuracy of hybrid quantitative weighing for packaging machines. With respect to the hybrid quantitative weighing system for the packaging machines featured by nonlinearity and time delay, the double-freedom-degree digital controller (RST controller) of a three-branch structure was constructed. Equivalent to a forward predictive controller and a no-time-delay controller, the RST controller could eliminate the effects of disturbances and delays on the system. A quantitative weighing control system for packaging machines based on RST was designed. The simulation comparison of traditional PID controller and PID-Smith controller was conducted with Simulink tool. The simulation results showed that, compared with the PID controller and the PID-Smith controller, the RST controller had less overshoot, shorter adjustment time, better tracking ability and stronger robustness. It could effectively improve the stability and control accuracy of the weighing control system for the packaging machines. The RST controller can improve the accuracy of hybrid quantitative weighing for packaging machines, so as to improve the packaging accuracy of the packaging machine.