With the increasing demand for the application of fiber coupled laser, the requirement for the coupling efficiency of fiber optic and laser laso increases. The positions of the focusing spots of laser with different wavelength are different. The position of the laser focusing spot is one of the important factors affecting the coupling efficiency, and it has certain practicability for the precise positioning of the laser focusing spot. A focusing combined lens group is designed to focus laser beam. The CCD camera is used to collect the images of the front and back laser focusing points. The acquired images are processed by MATLAB software, where the spot is fitted by circle and the diameter of which is calculated. The position of the minimum diameter is the focus position. The results show that the laser focus position with different wavelength is different and the relative errors of focal length are 0.59% and 0.73%, both the measured focus position and the size can be accurate to 0.001 mm. The method has the advantages of simple design, automaticity and accuracy, and especially in judging the focus position of the invisible laser.