Objective:To construct eukaryotic expression vector pIRES2-EGFP-C5a,prokaryotic expression vector pET-21a-C5a of rat complement C5a containing histidine tag,and observe its expression and biological activity in vitro. Methods:Total RNA was isolated from rat liver cells, C5a gene was amplified by reverse transcriptional PCR and inserted into pIRES2-EGFP vector. After lipofectamine-mediated transfection of HEK293 cells with pIRES2-EGFP plasmid,the expression of rat C5a protein was determined by fluorescence microscope and Western blot. The prokaryotic expression vector of pET-21a-C5a was constructed,and the expression of C5a protein was determined by Western blot. Rat C5a was purified by Ni2+ chelating affinity chromatography column. The reactive oxidative species(ROS) generated from neutrophils which were stimulated by C5a was detected by flow analyzer. The mRNA of IL-6 and TNF-α was detected after rat GMCs were stimulated by C5a for different time. Results:The rat complement C5a gene was amplified by reverse transcriptional PCR successfully. The pIRES2-EGFP-C5a plasmid was successfully constructed and tranfected into HEK293 cells. The expression of green fluorescent protein was seen under by fluorescence microscopy,but no C5a was detected. Meantime,the pET-21a-C5a plasmid was also constructed,and the expression of C5a could be detected using Western blot. And the histidine tagged C5a protein was purified by Ni2+ chelating affinity chromatography column. C5a can stimulate the nertrophils to generate ROS. Conclusion:The pIRES2-EGFP-C5a plasmid and pET-21a-C5a plasmid were successfully constructed,and the expression of C5a in prokaryotic expression vector pET-21a-C5a could be detected and the product was biological active.