The invention provides a master cylinder driving system of a heavy dual-function hydraulic machine. According to the master cylinder driving system of the heavy dual-function hydraulic machine, a large-flow oil supply pump, a small-flow oil supply pump and a variable oil supply pump which are arranged in parallel are adopted, the three oil supply pumps are cooperatively and respectively connected to a bypass oil discharge loop and a plunger cylinder through one-way control valves, in the use process, any one, two or three of the three oil supply pumps are selected according to the speed requirement of the plunger cylinder, and therefore the requirement of the plunger cylinder for high-pressure large-flow oil liquid in the vertical extrusion process can be met through rapid oil supply; a small-drift-diameter main oil path control branch and a large-drift-diameter main oil path control branch between an oil supply loop and the plunger cylinder are utilized, precise regulation and control of the speed of the plunger cylinder can be realized so as to meet the requirement of die forging for precise control over the high-pressure oil liquid flow entering the plunger cylinder, therefore, the foundation can be provided for achieving the two functions, namely die forging and vertical extrusion on the heavy hydraulic machine, the processing and manufacturing cost can be reduced, and the use efficiency of the single heavy hydraulic machine can be improved.