A voltage adjusting circuit includes a voltage regulator module (VRM), a control chip, a connection device, and a number of first resistors. The VRM includes an input receiving a first voltage from a motherboard, and an output connected to a liquid crystal display (LCD). A number of sense terminals of the control chip are connected to the LCD to sense current of the LCD. A driven terminal of the control chip is connected to a control terminal of the VRM to output corresponding driven signals to control the VRM to output corresponding voltage to the LCD. A first terminal of each first resistor is connected to a corresponding sense terminal of the control chip. A second terminal of each first resistor is grounded. The connection device is configured to cut off or connect the first resistor from or to the corresponding sense terminal of the control chip.