Studies on petrology and major and trace elements of Tianchi Volcano, Wudalianchi Volcano and Tengchong Volcano have been reported in recent years. This paper presents 18 sets of Sr-Nd isotopic data about these three volcanoes, and then discuss the nature of mantle sources and magma evolutions. Magma of Wudalianchi Volcano directly comes from mantle chamber, without any significant fractional crystallization and crustal contamination, and its mantle source is a mixture of EMI and PM. Samples from Tianchi Volcano of various stages show similar features close to PM, which suggests that there probably exist a huge crustal magma chamber beneath Tianchi Volcano, with continual mantle-derived magma replenishment. As to Tengchong Volcano, its high potassic calc-alkali magma source is a mixture of PM and EMII, resulting from crust-mantle interaction within the plate.