Abstract: The Southwest Yunnan Tin Belt is one of the most important tin metallogenic belts in China. The temporal and spatial distribution of granite-related tin deposits in the Southwest Yunnan Tin Belt has been summarized, but the relationship between the spatial distribution of tin deposits and the nature of the crust, as well as the reasons for controlling tin mineralization, are still unclear. In this paper, published zircon Hf isotope data of Early Paleozoic-Cenozoic granites in southwest Yunnan are collected. Based on previous large-scale isotope mapping of the Sanjiang Tethys orogenic belt, the ε_Hf(t) value and T_DM^C contour maps and two typical profiles in southwest Yunnan are drawn by ArcGIS software. The mapping results show that the Changning-Menglian orogenic belt and Baoshan terrane are ancient crustal domains with low ε_Hf(t) high T_DM^C, while the Tengchong terrane has uneven isotopic distribution, and there are both ancient crustal regions with low ε_Hf(t) and high T_DM^C, as well as newly formed crustal regions with high ε_Hf(t) and low T_DM^C. The distribution of tin deposits in southwestern Yunnan is closely related to crustal properties. Tin deposits are all distributed in ancient crustal areas with low ε_Hf(t) and high T_DM^C, while no tin deposits have been found in the newly formed crustal areas with high ε_Hf(t) and low T_DM^C. The concentrated production of tin ore in ancient crustal regions may be related to ancient tin rich crust. The mixing of low tin and high oxygen fugacity mantle magma has an inhibitory effect on the enrichment of tin in granite, which may be the reason for the unclear tin mineralization in the newly formed crustal area.