Preparation and purification method of monopolyethylene glycol recombinant human erythropoietin

The invention discloses a method for preparing and purifying monopolyethylene glycol recombinant human erythropoietin. The method comprises the following steps: modifying human erythropoietin with PEG (Polyethylene Glycol); preparing a cation exchange chromatographic column; diluting the modified product, and loading the diluted modified product to a cation exchange chromatographic column; carrying out gradient washing or isocratic washing by adopting a 0-30% acidic washing mobile phase to elute impure proteins on the cation exchange chromatography column; eluting by adopting a 40-80% acidic elution mobile phase in a gradient or isocratic elution mode, and collecting an elution main peak. According to the method disclosed by the invention, cation exchange chromatography filler is adopted, elution is carried out in an acid eluent environment, unmodified EPO and second-modified or multi-modified EPO are well removed, the purity of the monopolyethylene glycol recombinant human erythropoietin can be improved from