In this paper, a method for inspecting the defective lenses is proposed. Defects will not only affect the performance of the system, but also do harm to the experiment. Therefore, it is critical to find them out before lenses are used. The principle we adopted here is the laser diffraction and the light source we employed is a He-Ne laser whose diameter is closed to 0.5 mm when focused on the sample. Cooperated with the platform proposed, a convergent lens is placed to collect the diffracted light from the defects while the normal reflecting light is reflected by the mirror attached to it. Thanks to this, the diffracted light can be separated simply. In addition, a circuit module with the chip named max44009 is applied to detect the intensity of diffractive light. Compared to the intensity data obtained by the computer with the threshold we have set automatically, the machine could judge whether the defect is existing. Moreover, this method can detect lenses with various curvatures and calibers. Finally, the system performance is assessed by conducting a series of tests using commercial lenses.