Ultrasonic pest repellers are important devices for the control of rodent pests by physical methods. However, scientific and uniform methods for evaluating the efficiency of ultrasonic repellers in repelling pest rats are lacking. In this study, we tested the efficiency of one ultrasonic pest repeller on adult male Rattus losea under laboratory condition by comparing the rat number and food intake in two adjacent rooms with open or close repellers. Results showed that rat number and food intake in the room with open repeller were significantly lowere by 27% and 17%, respectively, than that in the room with a closed repeller after 7 days. The tested repeller had some efficiency on R. losea, but isn’t adequate for controlling rodent pests in room conditions.