The Mianhuakeng Uranium Deposit is one of the most important uranium base with complex mineralization conditions. In the paper, the characteristics of minerals have been systematically studied with the electron-microprobe in altered rock of the deposit. It sees that the minerals association is Pitchblende, Zircon, Parisite, Coffinite-Thorianite, Apatite, Xenotime, Allanite in the rocks. The main uranium resource minerals are Coffinite-Thorianite, Xenotime and Monazite. It has been a great impact on those minerals by hydrothermal mineralization when the deposit was formed, but it has been tended to decrease more uranium content in the minerals when closer to the ore body. Whole the monazite has been altered to the parisite, and the xenotime was been tended to alter to apatite, but Coffinite-Thorianite was altered to plumbothorite. In this alteration process, the minerals released of a large amount of uranium into the mineral-fluid. But apatite, zircon and allanite had a low level uranium so they were not the resource minerals.