This paper presents the design of an electronic scale based on STC89C52RC MCU, which uses resistance strain gauges as the bridge weighing sensor. Output voltage can be manipulated by the resistance of strain gauge, which is related to its strain. By establishing mathematical model, the output voltage forms linear relationship with the the object weight. The design utilizes the high precision conversion chip HX711 to amplify the weak voltage signal since the strain is very small. As a result, the object weight is displayed on a 12864 LCD. To meet practical demand, the electronic scale can realize the function of valuation and overload alarm.