The studies on PDI-, PP1- and chaperone-catalyzed refolding of recombinant human IL-2 and GM-CSF show that PDI can prevent the mismatch of disalfide bonds and formation of aggregates by interchains linkage, furthermore, PDI can correct, the mismatching of disulflde bonds in IL-2 isomers. PPI can increase the rate of folding reaction while chaperone can prevent the aggregation during the folding process. In addition, there is a synergistic effect between them. The studies on PDI-, PP1- and chaperone-catalyzed refolding of recombinant human IL-2 and GM-CSF show that PDI can prevent the mismatch of disalfide bonds and formation of aggregates by interchains linkage, furthermore, PDI can correct, the mismatching of disulflde bonds in IL-2 isomers. PPI can increase the rate of folding reaction while chaperone can prevent the aggregation during the folding process. In addition, there is a synergistic effect between them.