The invention provides a stirring cylinder discharging door self-tension adjusting system which comprises a discharging door, a bearing block plate, a hinge seat, an adjusting seat plate and a discharging door rotating body. The discharging door is fixed onto the bearing block plate, the hinge seat is arranged on the bearing block plate, the discharging door rotating body is fixed onto the hinge seat through the adjusting seat plate in a pivoting manner, a head is arranged at one end of the discharging door rotating body, a slotted hole is formed in the discharging door rotating body, a springis arranged at the head and faces the bearing block plate, and the slotted hole penetrates an angle adjusting bolt. The self-tension adjusting system is simple in structure and good in sealing performance.