Since non-contacting displacement sensors with high precision have been used widely, this paper presents one of examples, which is the spectral confocal displacement sensor. Firstly, the working principle of the sensor is described, and then the design and evaluation schema of the system is proposed. Finally, we design a specific case of the spectral confocal displacement sensor objective lens based on CODE V macro language and MATLAB. The sensor whose work-distance is 0~1.173 mm has the measuring accuracy better than 5 μm. The lens is combined with a single lens and doublet lens. In the work wavelength, each single-wavelength has the corresponding largest RMS radius of 2.8 μm. Through linear regression fitting of the defocusing amount and linearity of the wavelength, it is obtained that the coefficient of determination is 0.985 9. So the linearity of measurement is well.