In this paper, the authors conducted a study of the features of cell parameters and infrared spectroscopy of quartz and cassiterite at different ore-forming stages in the Lailishan tin deposit of Yunnan Province by using X-ray powder diffraction and infra-red spectroscopy and on the basis of detailed field investigation and petrographic research, so as to interpret the genetic information of quartz and cassiterite. The results show that the hydrothermal mineralization period of the tin deposit can be divided into four stages, i.e., mica-pyrite-topaz-granular cassiterite stage (Ⅰ), mica-quartz-pyrite-columnar cassiterite stage (Ⅱ), quartz-pyrite-radial cassiterite stage (Ⅲ) and fluorite-quartz-pyrite-sphaerolitic cassiterite stage (Ⅳ). From stageⅠ to Ⅳ, the values of a₀, c₀, V₀ and the c₀/a₀ ratios of the cell parameters in quartz show a decreasing trend. Axis ratio of the rate of change in quartz is from 0.773 07 to 3.496 88; the absorbance of each absorption peak of the infrared spectroscopy in quartz tends to increase. The authors infer that quartz mainly has substitution impurities such as Al³⁺ and Fe³⁺ at stage Ⅰ and Ⅱ, has substitution impurities and interstitial impurities at stage Ⅲ, which is complicated, and has interstitial impurities such as Na⁺, K⁺ at stage Ⅳ. The values of a₀, c₀ and V₀ decrease firstly and then increase in cassiterite with the evolution of the ore-forming stage, and are smallest at stage Ⅱ, which is consistent with the changes of the total amount of impurity elements in cassiterite at different ore-forming stages. These phenomena suggest that changes of cell parameters in cassiterite are mainly affected by mixed impurity elements in lattice rather than temperature. The characteristic infrared spectra of cassiterite at different ore-forming stages are similar and belong to the deformation spectra, implying the characteristics of cassiterite-sulfide hydrothermal deposits. Moreover,the composition of hydrogen and oxygen isotopes in quartz shows that the ore-forming fluid is a mixture of magmatic and meteoric water, and the initial ore-forming fluid is derived from magma. With the evolution of hydrothermal solution, meteoric water enters hydrothermal solution along the tectonic fissures, which makes the isotopic composition of hydrogen and oxygen shift to atmospheric water.