An exemplary system for testing a serial port includes a serial port (106), a female cable connector (108) connected to the serial port, and an optical-coupled chip (110) connected to the female cable connector. The serial port, the female cable connector and the optical-coupled chip collectively form a circular loop. The system further includes a transmitting module (124), a receiving module (126) and a determining module (128). The transmitting module is configured for transmitting data into the circular loop. The receiving module is configured for receiving data from the circular loop. The determining module is configured for comparing the transmitted data and the received data, and determining whether the serial port is in predetermined working condition according to the comparison result. A related method is also provided.