An embodiment of the invention discloses an electrical power system gas relay oil level indication method and device, and aims to solve the technical problems that current inspectors are difficult to distinguish the condition that the inside of a gas relay is fully filled with oil or the oil in the gas relay is insufficient as transformer oil is transparent and colorless when examining oil level through an observation window of the gas relay on the ground. The method includes the steps: acquiring the sizes of an observation window and a baffle plate of the gas relay according to the type of the gas relay; calculating the width of a first marking line arranged on a diagonal line of a baffle plate, and calculating the distance between the observation window and the rear baffle plate according to the installation height of the gas relay; calculating the position of a second marking line arranged on the surface of the observation window; setting a monitoring point below the gas relay according to position relations between the first marking line and the second marking line, and acquiring oil level conditions of the gas relay through the monitoring point. The baffle plate includes a rear baffle plate.