Abstract: Response regulator is a very important component in His_Asp phosphore lay signal transduction pathway. A given response regulator controls the downstream genes by acquiring a phosphoryl group from the sensor to its conserved aspartate residue in response to environmental stimuli. 14 members of the response regulators, which can be classified into two distinct subtypes, have been discovered in the higher plant Arabidopsis thaliana. In aspect of structure design, the type_B may serve as transcription factors because of the containing of B_motif and the relatively large C_terminal extension. The expression profile of type_A response regulators that are cytokinin_ and nitrate_inducible is also different from that of type_B. In aspect of biochemical properties, type_A response regul ators appear to have a strong phosphohistidine phosphatase activity while those belonging to type_B may function as phosphodonor for AHPs.