The invention discloses a self-adaptive distance protection method. The method comprises the following steps of calculating fault current and voltage, fault transient state component and system line impedance ratio SIR in real time after the system breaks down; calculating measurement errors of an underreach distance element according to a calculation result of the first step; dynamically adjusting an actuation range of the underreach distance element according to a calculation result of the second step; calculating an actuation fuzzy region of the underreach distance element according to the calculation result of the first step; dynamically adjusting actuation anti-shaking time of the underreach distance element according to a calculation result of the fourth step; and according to calculation results of the third to fifth steps, judging whether the underreach distance protection satisfies a distance protection motion logic, if yes, the underreach distance protecting an actuation exit. Through adoption of the method, the problem bothering the power system industry that how short a line can be used in underreach distance protection is solved, and the underreach distance protection is guaranteed not to exceed when being applied to any lines, so that the workload of staffs for fixed value setting is greatly reduced, and the operation reliability of the system is improved.