In order to study the color-genetic mechanism of brown jade, samples collected from Xinjiang were studied using XRD, ICP-MS, Raman and HRTEM. The results are as follows: the main mineral composition of brown jade is tremolite. ICP-MS data show that the concentration of the brown color has a good relationship with Fe element, samples with deeper color have higher Fe content. Fe occurs as iron mineral distributed in the tremolite particles or the microcracks. The grain size of the muddy iron mineral is extremely small, and the content is low. Experiments were designed to enrich the iron mineral with Stokes law. Then we studied the enriched samples with TEM and got the electron diffraction patterns of iron mineral, and identified them to be goethite. We conclude that the brown coloration of nephrite is due to goethite distributed in the tremolite particles or the microcracks. Raman spectra show that the rare mineral particle at the surface of the sample is rutile, and because of the low content, rutile has a little influence of the coloration.