Abstract: Aiming at the problems existing in the verification of relay protection device settings before and after maintenance, this paper proposes a new method for checking the definite values, which is based on the ESC/POS printer interface transmission specification, and can obtain the operating value data from the protection device printing interface and parse it to form a text file to realize the paperless printing of the definite values of the relay protection devices. The text file is stored by site, interval and equipment, and compared with the printed value file before the maintenance work, so that the verification of the values before and after the maintenance work can be done quickly and accurately. The method is practical, safe and reliable through actual application and system verification, which ensures the validity of the main grid equipment value checking and is of practical significance to ensure the safe and stable operation of the grid.