The invention discloses a preparation method of recombinant 
human insulin, which relates to the 
protein polypeptide type 
medicine field. The technical problem needed to be solved by the invention aims at providing a preparation method for 
Escherichia coli to express the recombinant 
human insulin in order to overcome the technical disadvantages in the prior art of using the poisonous and harmful substance CNBr and having a complex production process. The preparation method for the recombinant 
human insulin of the invention comprises the steps of: 
thallus crashing, inclusion body dissolving, 
proinsulin sulfonating, purifying 
proinsulin, and 
proinsulin renaturation, 
enzyme cutting transmission, etc., and the preparation method is characterized in that during the inclusion body dissolving process, the -SH of proinsulin is transformed into -SSO3<->, and then human 
insulin is obtained through purifying the sulfonated proinsulin, reduction renaturation and 
enzyme cutting transmission by positive 
ion, and then through the negative 
ion exchange layer purification. The preparation method of the recombinant human 
insulin of the invention does not use the CNBr and has simple technique with high human 
insulin yield coefficient and purity.