To investigate the function of plant plasma membrane, proteins of rice plasma membrane were analyzed and the proteins changed by cold stress were identified. Plasma membrane proteins were purified with an aqueous two-phase partitioning method from root of rice seedlings, and activity of specific H -ATPase localized in plasma membranes was measured. The plasma membrane proteins were separated by SDS-PAGE or 2D-PAGE, and analyzed with nano LCMS/ MS. The number of transmembrane helices was predicted from the amino acid sequence of annotated proteins. Functional categorization revealed that the most of proteins were associated with energy production, signal transduction, protein synthesis, cell growth/division and defense. In addition, 12 cold stress responsive proteins were identified from the plasma membrane using 2D-PAGE based proteomics method. Out of them, cold shock protein-1 was significantly decreased in plasma membrane of rice under cold stress.