Abstract: [Objective and Method]The aim of this paper was designed to study the effect of different induced time,induced dose IPTG final concentration,culture temperature,rotation speed of shaker on the expression level of sheep β_2-adrenoceptor gene,the second extracellular loop recombinant plasmid pET32C-AR/Se harboring in order to select and screen the best culture conditions.[Result]The results showed that along with prolonging of IPTG induction time, the relative expression level of the recombinant protein increased gradually and reached the peak 2 h later, counting for 30.1; of the total bacterial protein. The expression level of the recombinant protein was between 27;～30; of total bacterial protein when the final concentration of IPTG ranged from 0.01 to 2 mmol/L. The crest value of expression level was 30.5; of total bacterial protein when the final concentration of IPTG was 0.01 mmol/L. In four culture temperatures, the expression level of the protein reached the peak, 35.5; of the total bacterial protein at 25℃. When the rotation speed of shaker ranged from 100 to 200 r/min, the expression level of the protein fluctuated between 33;～40;. The highest expression level of the foreign protein reached 200 r/min, counting for 40; of the total protein. [Conclusion]From the results, the conclusions could be drawn that the optimum culture conditions for expression of the second extracellular loop of sheep β_2-adrenoceptor in E.coli BL21(DE3) when the recombinant bacteria grow to OD_(600) 0.5 in LB fluid medium, IPTG added to a final concentration of 0.01 mmol/L, and induced at 25℃ and 200 r/min for 120 min.