The invention discloses a hydraulic dynamic brake operating system for a tractor. The hydraulic dynamic brake operating system mainly comprises an oil suction filter, an oil pump, an overflow valve, a check valve 1, a throttling port, a high-pressure oil filter, a liquid filling valve, a pressure gauge, an accumulator, a brake low pressure alarming switch, a dual-circuit dynamic brake valve, a left dynamic brake valve, a shuttle valve, a check valve 2, a brake taillight pressure switch, a right dynamic brake valve, a pressure setting piece and a pressure compensator. The hydraulic dynamic brake operating system is characterized in that the oil suction filter is arranged in an oil tank of the tractor; the oil pump is arranged on one side of the tractor; the oil suction filter is connected with the oil pump through an oil pipe; the liquid filling valve is arranged on one side of the tractor, and is connected with the oil pump through a pipeline; and the dual-circuit dynamic brake valve is mounted on the bottom plate of a driving cab, and is connected with the liquid filling valve through an oil pipe. The system eliminates other pumping sources by dint of the hydraulic steering system of the tractor, and fully meets the requirements on the brake of the whole tractor and the braking performance of a high-power tractor. The structure of the system is compact and meticulous.