Abstract: In order to study the physiological function of MAPKKK in Dunaliella salina (DsMAPKKK), the open reading frame (ORF) of DsMAPKKK gene was amplified by RT-PCR. The prokaryotic expression vector pGS21a- DsMAPKKK was constructed by using T4 ligase to link the ORF of DsMAPKKK and the vector pGS21a. Then the recombinant plasmid was introduced into E. coli BL21 (DE3) and induced by IPTG. The fusion protein was expressed successfully in E. coli BL21. Detected by SDS-PAGE, the fusion protein had existed in both supernate and inclusion body. The soluble protein was purified through GST column, electrophoretic analysis showed that there was a single protein band at about 68 kD, indicating that the fusion protein had been effectively purified. The result of western blotting demonstrated that there were obvious hybridization bands at about 68 kD, preliminarily demonstrated that the purified protein was DsMAPKKK protein with a GST label. The successful expression and purification of DsMAPKKK laid a solid foundation for further exploration of the nature and function.