This paper has dealt with chemical composition trace elements characteristic parameters and crystallochemical structure of biotite in Yangxi granite body. Biotite in Yangxi granite body is 1 M polytype ferruginous biotite. Chemical composition of all biotite samples from Yangxi granite body is similar to each other with the exception of No. 16-12 sample, which has more Al, Mn and less Si，Ti.Special chemical features of biotite from Yangxi granite body are consistent with features of biotite from South China granites.KAl(KAl=Al/Si+Al+Fe+Mg)values range between 0.19 and 0.23，averaging 0 .2112; K/Na ratios range generally between 10.5 and 19. 6, averaging 19.5470 ; MF(MF=K+ +Na + /Ca+ Mg) values range generally between 0.70 and 0.96，averaging 0.9014 ; m(m=Mg/ Mg+∑Fe+Mn)values are generally between 0.364 and 0.389， averaging 0. 3509. Tetrahedral ions of biotite from Yangxi granite are Si4+ and A13+，whereas Fe2+ and Mg2+ are the major octahedral ions. Interlayer ions are K+，Na+ and Ca2+.The average b0 value is 9.238A.The average c0 value is 10.035A. Characteristics of biotite from Yangxi granite show that the granite is of crystal transforrnation type probably mixed with small amounts of mantle materials. The No. 16一12 sample collected near a Nb, Ta mineralised spot has more Al, Mn and less Si，Ti，with m value being 0.2037，which is much lower than the average m value. Its KAl value is 0.272， which is considerablyhigher than the average KAl value. Its MF value is 1.4769,which is also remarkbly higher than the average MF value. Samples taken near the scheelite ore deposit show little difference from those taken far away from the scheelite ore deposit. Their biotite only has a bit higher Ti content and slightly lower K and Va content， suggesting that the constituents of the granite body have little to do with the scheelite deposit.