Minerals of the pyrochlore-microlite group belong to principal Nb, Ta accessory minerals in the Beauvoir granite, France. Most of their grains are euhedral with colors ranging from white,yellowish to greenish. Their sizes vary from microns to millimeters. Microlite is absent in the BIII facies and rare in the BII facies, but very abundant in the BI facies; pyrochlore appears only at the top of the Beauvoir granite. Over 30 electron-microprobe analyses arc consistent with the general crystalchemical formula: A2-mB2X6Y1-n.pH2O, where principally A=Ca, Na, U; B=Nb, Ta,W,Sn,Ti; X=O; Y=F, OH. The hydration often appears at the rim or along micro-fracture in grains of pyrochlore-microlite, acompanied by leaching of Na, Ca, U from the A site and of F from the Y site, and by the introduction of K, Ba into the A site. The Nb/(Nb+Ta)ratio of the pyrochlore-group minerals has an increasing tendency upward in the granite body. These minerals are generally rich in uranium, the highest percentage found of UO2 is 15.05%.On the one hand,certain pyrochlore-microlites may be considered as uranpyrochlore-uranmicrolite, and on the other hand, rnicrolite of the lower part contains on average 6.3% UO2; in contrast, microlite and pyrochlore of the upper part have the mean content of 9.0%. Pyrochlore-group minerals show zoning structure, due chemically to the oscillatory variations in Nb and Ta. At the top of the granite, minerals of this group may replace manganocolumbite, leading to the formation of a special replacement structure related to the late stage subsolidus interaction between magma and meteoric fluid.