It is important in expressing,purifying and analyzing crucial protein in vivo of solfataricus for the study of important life activities of extremely thermophilic archaea.The over-expression vector is constructed on the basis of pZC1 and pEXA vector inserted by araS promoter.Mre11 with 6×His-tag in C-terminal are expressed successfully using it.Rad50 which interplays with Mre11 is detected by co-purification.And it is ensured that the frame of the complex is still unchanged in high concentration of salt （500 mmol/L NaCl）.It indicates that the complex still keeps the function of DNA repair in adverse situation.Further analysis of co-purification makes it clear that genome DNA fragments are the essential condition of foming the MR complex.In the absence of genome DNA fragments,the molecular chaperone of archaea may bind and protect Mre11.So this expression system possesses important sense in identifying the interact network of protein in vivo.