This paper presents the optical system design for a high precision, temperature measuring, Raman lidar spectrometer. Using an aspheric lens group on an imaging spectrometer with spherical aberration correction, the results show that the pure rotational Raman spectrum imaging deviation can be effectively suppressed. The 10 mm/nm line resolution requirements for a high precision spectrometer, with a double grating structure design, and the temperature parameters of a Raman spectrometer for ray tracing, are fitted with a double grating incidence angle, and optimal values for the collimating and focusing lens focal lengths. The optimization results were substituted into the Zemax software for simulation analysis, and showed that a single spectral imaging width control in 0.771 5 mm, with 0.1 nm intervals of pure rotational continuous spectrum imaging center spacing, can reach 1 mm. By calculating the purely rotating Raman backscattering signal at J=6, the Rayleigh-Mie scattering signal was suppressed by 108, satisfying the requirements of the linear array detector for image quality, and achieving the high precision of the pure rotational Raman lidar. This has solved the issue in which the double grating spectrum technique could not reach to extract the 355 nm band, which is the accuracy requirement of the high, pure, rotational, Raman spectrum. This indicates that the temperature measurement ability of the Raman lidar technology development is of far-reaching significance, and provides a more accurate basis for the analysis of urban heat island effect, and environmental pollution sources.