Multi-spectral radiation temperature measurement technology is one of the most powerful tools in high-temperature measurement because of its advantages of no interference to the measured field, no upper limit of measurement and fast response speed. At present, the multi-spectral pyrometer mainly measures point temperature. The optical path radiates the point to be measured through the objective lens, diaphragm, prism and other optical paths and then enters the detector array to realize the multi-spectral information collection at a single point. As industrial intelligence degrees unceasing enhancement, more need to obtain real-time information, a large number of temperatures of special metal materials such as the smelting process, high-temperature alloy laser automatic welding process, the semiconductor crystal growth process, the rocket launch the tail jet flame temperature diagnosis in areas such as all need to obtain real-time and even the entire two-dimensional temperature on the surface of a line, to improve product performance and quality. Therefore, it is very important to measure the temperature distribution of a line on the surface by multi-spectral radiometry. However, when the aperture is changed into a slit to realize the radiation splitting on the surface of the line to be measured through the traditional optical path such as lens and prism, the spectrum of the slit will be severely bent due to off-axis transmission due to the spherical aberration of the optical system, which is not good for the complete reception of the rectangular photoelectric detector array. Therefore, a multi-spectral line temperature and light path system based on an orthogonal cylindrical lens group is proposed in this paper. The special function from the circle to ellipse and straight line can be realized by using the orthogonal cylindrical lens in different positions, which better solves the spherical aberration problem existing in the light path of traditional multi-spectral radiation pyrometer. Using ZEMAX optical design software, the reverse optical system is designed based on the size of the s4111-16Q photodetector array. The parameters of key optical devices such as slit, objective lens, prism and orthogonal cylindrical lenses are determined. Based on the actual optical devices processed by these parameters, the optical system of multi-spectral line temperature pyrometer is built. The results show that the image of the slit is obviously bent without the orthogonal cylindrical lens, and the image of the slit is obviously bent without the orthogonal cylindrical lens, and the image of the slit is straight when the orthogonal cylindrical lens is added. It provides technical support for the spectral radiation information of the whole line to be integrated into each detector array, thus providing powerful spectral radiation data information for subsequent line temperature measurement.