The invention relates to a method for on-line verification of a relay protection setting value of a regional power grid. According to the method, the regional power grid is divided into multiple subareas according to the practical situation of operation of the regional power grid; a power grid model is established according to the subareas on a software platform, and the power grid model of the subareas is updated according to the real-time data and the practical operation mode of the power grid; a prediction failure set is established for each subarea; fault calculation is carried out on each predication failure in the prediction failure set, the numbers of broken-down electric devices under various situations are obtained, the action situations of a protection device are analyzed accordingly, and the current protection setting value of the power grid is verified. The sensitivity, the safety level and other quantity indexes of the currently operated relay protection setting value of the power grid can be obtained with the method. According to the method, the safety level, or called as the safety margin, of the currently operated relay protection setting value of the power grid can be obtained through calculation, and namely, the safety margin means the order of severity of the power grid fault which enables the current relay protection setting value to make the protection device operate by mistake or not operate.