A circuit board testing system includes a testing fixture and a computer system. The testing fixture includes a contact element, a switching circuit, a connection module, and a data acquisition unit. The contact element is connected with a circuit board. The switching circuit is connected with the contact element. The connection module is connected with the circuit board and the computer system. Consequently, an electric power is transmitted from the computer system to the circuit board through the connection module. By enabling the connection module, the data acquisition unit acquires a real voltage value corresponding to the electronic component. The computer system is connected with the testing fixture. According to the real resistance value, the computer system judges whether the electronic component passes the test.