The invention relates to a micro-tension control system and method of a hydraulic tension warm rolling mill, and belongs to the technical field of tension control of hydraulic tension warm rolling mills. The micro-tension control system comprises a left tension hydraulic cylinder, a left hydraulic system, a right tension hydraulic cylinder and a right hydraulic system. Each hydraulic system comprises a proportional overflow valve, a servo valve and a proportional pressure-reducing valve. In the stage that tension of a rolled piece is established, the stage that the rolled piece is rolled, and the shutdown stage that pass rolling ends, the opening and closing states of the left proportional overflow valve, the left servo valve, the left proportional pressure-reducing valve, the right proportional overflow valve, the right servo valve and the right proportional pressure-reducing valve are controlled, corresponding control quantities are set for the valves, and therefore the tension hydraulic cylinders can conduct tension closed-loop adjustment through the proportional pressure-reducing valves and tensiometers, or through the proportional overflow valves and the tensiometers. In the feeding and discharging stages of the rolled piece, the tension hydraulic cylinders conduct position closed-loop adjustment through the servo valves and displacement sensors. According to the invention, the tension control mode is simpler and more efficient, the tension control accuracy is effectively guaranteed, and micro-tension rolling of high-fragility or difficult-to-deform metal strip materials is achieved.