Collagen is expressed by gene-engineering for significant medical and biotechnological importance. In purification of collagen, ion exchange, widely used to purify and separate collagens, is a high capacity, cheap, efficient and rapid method for purification of collagen. Here we develop a single step system for purification of recombinant collagen which improves purification of collagen. In this experiment, the effects of parameters such as pH, salt type and salt concentration on the chromatographic behavior of recombinant collagen from E.coli on the cation-exchanger were evaluated with the aim of optimizing the ion-exchange purification of collagen. The collagen yield was also taken consideration in purification by the resulted lyophilized collagen. We describe the purity of recombinant collagen using SDS-PAGE gel electrophoresis and size-exclusion chromatography. All in all, the results demonstrate that single step purification may achieve high purity collagen and reduce the cost. And purified collagen can be used as the study of structure and preparation of biomaterials.