The Taiping-Huangshan batholith in southe ast China is a poygenetic composite granitoidconsisting of two parts. The northetn part is known as the Taiping granodiorite, geneticallydesignated to the Syntexis-type granitoids of southeast China or I-type Based onwhole-rock Rb-Sr isochron dating, its age is 22 3 m. y. with a relatively low initial Sr ratio(0.7069), suggesting that it was emplaced during the Indosinian period. The southern part,the Huangshan multi-staged granite, is genetically ascribed to the transformation type of south-east China, or S-type, which includes two bodies known as the Huangshan and Shiailin gran-ites. Both were formed in the late Yenshanian period as indicated by their ages: 131 m.y.for the Huangshan granite and 123 m. y. for the Shizilin granite, and high inihal Sr ratios(0.714 for the Huangshan granite and 0.718 tor the Shizilin granite) determined using whole-rock Rb-Sr isochron dating method. The biotite in the Taiping granodiorite is Mg-biotite witha high Mg/(Mg + ∑Fe + Mn + ~(VI)Al~(3+)) ratio (>0.42) in its octahedral layers, andhas a longer c-axis (10.220--10.224 A) and a larger unit-cell volume (499.5 A~3), as calculatedfrom X-ray powder diffraction data But the biotites in the Huangshan and Shizilin granies oc-cur mostly as siderophyllite, subsequently as Fe-biotite and occasionally as zoned mica consi-sting of siderophyllite and musco-vite. The Mg/(Mg + ∑Fe + Mn + ~(VI)AI~(3+)) ratios are low,while ~(VI)Al~(3+)/ (Mg+∑Fe+Mn+~(VI)Al~(3+)) ratios high in their octahedral layers. They have ashorter c-axis (10.128--10.196A) and a small nit-cell voume (494.5 A~3 on average). Compari-son of their chemical compositions and corresponding unit-cell parameters for 13 samples fromthe batholith indicates that the c-axis length increases with increasing Mg content with a noticeable positive correlation between them, but decreases with increasing ~VAI~(3+) content, showing anobvious negative correlation. The changes of the b-axis lengths with the compositions of biotitesare much less pronounced than that of the c-axis length. The Taiping-Huangshan batholith in southe ast China is a poygenetic composite granitoid contrasted of two parts. The northetn part is known as the Taiping granodiorite, genetically designed to the Syntexis-type granitoids of southeast China or I-type Based on whole-rock Rb-Sr isochron dating, its age is 22 3 my with a relatively low initial Sr ratio (0.7069), suggesting that it was emplaced during the Indosinian period. The southern part, the Huangshan multi-staged granite, is genetically ascribed to the transformation type of south- east China, or S-type, which includes two bodies known as the Huangshan and Shiailin gran-ites. Both were formed in the late Yenshanian period as indicated by their ages: 131 myfor the Huangshan granite and 123 my for the Shizilin granite, and high inihal Sr ratios (0.714 for the Huangshan granite and 0.718 tor the Shizilin granite) determined using whole-rock Rb-Sr isochron dating method. The biotite in the Taiping granodiorite is Mg-biotite witha high The Mg / (Mg + ΣFe + Mn + ~ (VI) Al ~ (3+)) ratio (> 0.42) in its octahedral layers, and has a longer c- axis (10.220-10.224 A) and a larger unit- cell volume (499.5 A ~ 3), calculated as X-ray powder diffraction data But the biotites in the Huangshan and Shizilin granies oc-cur mostly as siderophyllite, subsequently as Fe-biotite and occasionally as zoned mica consi-sting of siderophyllite and musco- Vite. The Mg / (Mg + ΣFe + Mn + ~ (VI) AI ~ (3+)) ratios are low, while ~ (VI) They have ashorter c-axis (10.128--10.196A) and a small nit-cell voume (494.5 A ~ 3 on average). Compari-son of their chemical compositions and corresponding unit-cell parameters for 13 samples from the batholith indicates that the c-axis length increases increases with increasing Mg content with a noticeable positive correlation between them, but decreases with increasing ~ VAI ~ (3+) content, showing anobvious negative correlation. changes of the b-axis lengths withthe compositions of biotitesare much less pronounced than that of the c-axis length.