Abstract: Tapiolite is a rather rare Ta mineral occurring particularly in highly differentiated granitic pegmatites． The occurence of tapiolite from the Koktokay No.3 granitic pegnmtite dyke，Altai，Xinjiang Autonomous Region，is reported in this paper．The tapiolite，as anhedral crystals，is associated with manganotantalite(including manganotantalite I and manganotantalite II)and uranmierolite，forming Nb-Ta mineral aggregate．The manganotantalite I is the main component of the aggregate，whereas the tapiolite associated with the manganotantalite II occurs typically in the rim of the aggregate．RTa[RTa=Ta/(Nb+Ta)]of tapiolite varies between 0.96 and 0.99，while RMn[RMn=Mn/Fe+Mn]]ranges between 0.10 and 0.21．Based on assemblage and compositional feature of Nb-Ta minerals．it is suggested that tapiolite was a product of exsolution from the metastable phase which was the remnant of manganotantalite I crystallization under disequilibrium condition．