The LuxR-LuxI-type quorum sensing systems have been shown to play a key role for rhizobia to form nodules on their plant hosts. The protein MrtR in Mesorhizobium tianshanense is a Lux-type regulator and regulates the LuxI-type synthesis, MtrI, in the quorum sensing system of M.tianshanense. The mrtR coding sequence was fused to the T7 promoter of bacteriophage T7 by PCR amplification, using M.tianshanense genomic DNA as template. The resulting PCR product was cloned into pALEX, resulting in co-expressed GST-MrtR plasmid pALEX-mrtR. The resulting plasmid pALEX-mrtR was transformed into Escherichia coli strain BL21/DE3. High quantity of soluble GST-MrtR was obtained when the recombinant E.coli strain was incubated at 37℃ with IPTG inducer. The protein was purified by GST affinity chromatography and tested by SDS-PAGE. The polyclonal antibody against MrtR was obtained. The ELISA titer of antiserum against MrtR was about 1∶262000. Western blot analysis showed that the antiserum could bind to the expressed fusion protein specifically.