The invention discloses a load pressure self-adaptive control hydraulic system, a control method and a pre-grooving machine. The load pressure self-adaptive control hydraulic system comprises an oil supply main path and a feedback auxiliary path. The oil supply main path comprises an electromotor, a balance valve set, a shuttle valve, an oil pump control valve, an oil tank, an oil pump, a filter, an electro-hydraulic directional valve and a motor, wherein the oil tank, the oil pump, the filter, the electro-hydraulic directional valve and the motor are connected in sequence. The oil pump control valve is suitable for controlling the oil discharge amount of the oil pump. The feedback auxiliary path comprises a throttling valve and an inverse-proportional relief valve. One end of the throttling valve is communicated with the liquid discharge end of the filter, the other end of the throttling valve is communicated with one end of the inverse-proportional relief valve, and the other end of the inverse-proportional relief valve is communicated with the oil tank. According to the load pressure self-adaptive control hydraulic system, the throttling valve and the inverse-proportional relief valve constitute the feedback auxiliary path, and thus the oil pump can be made to be in a constant pressure state, and the control requirements for torque self-adaption and flow self-following are met; accordingly, the motion stability of equipment can be improved, and the reliability of the equipment is improved.