Abstract: Through analyzing the chemical composition and characteristics of rock mineralogy of Guizhou nephrite and other typical ones by optical microscopy, scanning electron microscopy, XRD and WDXRF, the main mineral composition of Guizhou nephrite is tremolitite with the secondary mineral compositions of quartz and calcite. In addition to tremolitite as main composition, there is a small amount of isomorphous substitution; mixing of iron is a key factor to influence the color of Guizhou nephrite which is significantly different from other typical nephrites. These results provide a partial explanation to Guizhou nephrite apparent characteristics.