Our research selected the RNF149, the novel ubiquitin ligase which owned the high identity to GRAIL and belonged to the typeⅠ transmembrane protein, as our object. By the confocal laser scanning microscope, it was demonstrated that RNF149 is located at lysosome and the RNF149 is co-located with CD9. The interactions between RNF149 and CD9 were demonstrated by immune co-precipitation.RNF149 polyubiquitinates CD9 via ubiquitin Lys-48. The HeLa cells were co-transfected with the same quantity of the CD9 plasmids and the gradient increase quantity of the RNF149 plasmids. We found that the exogenous quantity of CD9 was decreasing with the increased expression of the exogenous RNF149. In HEK293T cells, the knocking down RNF149 by shRNA led to the increase of the endogenous CD9. All these evidence suggested that CD9 maybe regulated by RNF149. In addition, the knocking down RNF149 by shRNA led to the inhibition of the cell proliferation in HEK293T cells. This phenomenon suggested that the RNF149 possibly could be considered as the regulatory factor of the cell proliferation.