A server rack includes a main body, an electronic scale, and an alarm. The main body is used for receiving a number of servers. The electronic scale includes a pressure sensor and a microcontroller. The main body presses on the pressure sensor so that the pressure sensor can measure the pressure from the main body to obtain a pressure signal. The microcontroller analyzes the pressure signal to calculating the total weight of the main body and the servers. The alarm stores a predetermined weight threshold, which is the total weight of the main body and the maximum servers that the main body can bear. The alarm also compares the measured total weight with the predetermined weight threshold. When the measured total weight is larger than the predetermined weight threshold, the alarm alarms.