A lens auto-focusing method in camera module testing includes the following steps: providing testing equipment including a range finder, a signal processor and a driving member; providing an imaged object (20); providing an camera module including a lens module (10) and an image sensor, the view angle and the biggest value of the modulation transfer function of the lens module are both certain values, the image (30) of the imaged object is formed in the image sensor; the imaged object and the image formed thereby in the other side of the lens module are fixed; the imaged object and the image formed in the other side of the lens module are fixed; inputting an image distance tested by the range finder into the signal processor, the signal processor calculates a displacement for the driving member; the driving member drives the lens module to a focusing point.