The lens module is widely used in many types of equipment, such as mobile phone, image recognition product, iPad, computer camera module, security product, car rear view module, industrial endoscope and medical endoscope product. In the process of appearance quality inspection of lens module, it is a problem that the inspection accuracy depends mainly on manual workers. To save the time and amount of this quality detection labor, it’s necessary for us to design the lens module’s appearance quality automatic inspection system. This paper proposes a subpixel-accurate edge detection algorithm based on wavelet transform with the cubic spline interpolation for the lens module’s appearance quality inspection system. Firstly, calculate the wavelet modulus maximum, and detect a pixel-accurate edge. Then apply the cubic spline interpolation to obtain subpixel-accurate edge at the side of the pixel-accurate edge. Finally, an industrial measurement method using this subpixel-accurate edge detection algorithm is studied, and some experiments are conducted to demonstrate the effectiveness of the lens module’s appearance quality inspection system. Comparing with the traditional methods, the lens module’s appearance quality inspection system has a good anti-noise performance and stable inspection accuracy.