A method for controlling an auto macro function of a lens module is provided. Firstly, a control switching module is provided. The both terminals of the coil of the lens module are connected to a power source and the control switching module, respectively. In response to a first signal state of a control signal, a constant current is transmitted from the power source to the coil. The magnets attached on the magnet yoke provide a permanent magnetic field, and the constant current passing through the coil causes a magnetic force to be generated on the coil while moving the lens holder toward the magnet yoke by a constant distance. In response to a second signal state of the control signal, the power source stops transmitting the constant current to the coil, wherein a restoring force generated by the deformed spring causes the lens holder to return to its original position.