The basalts of Woniusi Formation at Baoshan area, located in western Yunnan Province, are composed of low-TiO2 tholeiites generally similar to the low-Ti tholeiites from Emeishan large igneous province. They are highly-differentiated magmatites rich in large ion lithosphere elements and high field strength elements, have significant Zr and Hf positive anomalies as well as high87Sr/86Sr and low143Nd/144Nd ratios, and show characteristics similar to those of continental-rift basalts. Geochemically it consists of three eruption cycles which can be divided into three rock units. The early-stage unit 1 basalts are characterized by massive plagioclase-phe-nocryst basalts, amygdaloid basalts and basaltic tuff. The middle-stage unit 2 and the late-stage unit 3 consist of minor olivine basalts and trachybasalt as well as diabase dykes. From the similar geochemical and Sr-Nd isotopic features with Emeishan basalt, they are interpreted as the products that evolved from the same parent magmas and experienced crystal differentiation of plagioclase and clinopyoxene. Their parent magmas were generated from an enriched lithosphere mantle associated with mantle plume. This suggests that the Emeishan large igneous province may have remarkable westward extension.