Based on statistical analysis of large quantities of geochemical data collected in western Yunnan, this paper gives a detailed summarization of the distribution pattern of Sn-related elemental anomalies and anomaly associations along the Western Yunnan tin ore belt and then classifies geochemical anomaly associations and divides geochemical zones in western Yunnan. It names this area"Western Yunnan geochemical proviuce"and delineates ten geochemical zones, thus providing geochemical basis for further research on tin deposfts in western Yunnan or even in its northward extension to Tibetan area.