Rare codon and mRNA secondary structure of translation initiation region were analyzed. Four bioengineered bacterium BL21(DE3)/pET-Mx, Rosseta (DE3)/pET-Mx, BL21(DE3)/pGEX-Mx, and Rosseta (DE3)/pGEX-Mx were obtained. Through optimizing the rare codon and mRNA secondary structure of translation initiation region, Mx protein was expressed in Rosseta (DE3)/pET-Mx, and Rosseta (DE3)/pGEX-Mx. The specified product of 75 kDa was detected by means of Western blotting analysis. The result showed that Rosetta (DE3) strain expressing some rare codon used in our experiment can obtain Mx protein expression, and the lower energy of mRNA structure can improve the expression level of Mx protein. This is the first report on the expression of the full open reading frame of Mx gene.