Recombinant human granulocyte macrophage colony stimulating factor (rhGM-CSF) is the major stimulatory cytokine.However, rhGM-CSF expressed in E.coli exists as inclusion body inside the cell.Because of being inactive in the denaturant solution, such as 7.0 mol·L-1 GuHCl or 8.0 mol·L-1 urea, it is necessary to refold or renature the denatured rhGM-CSF before further separation and purification.The usually employed methods for the renaturation of inclusion body proteins include dilution and dialysis, through these methods, the mass and bioactivity recoveries of target protein obtained are very low to be 5-20%.