Chinese hamster ovary cells (CHO) are preferable to prokaryotic, yeast or insect cells as hosts for biopharmaceutical production due to the products are more similar to their natural conformation. However, CHO cells confront tremendous difficulties when cultured in large scale such as mal-adaptation to serum-free medium, apoptosis and over-growth without limitation. So in addition to optimizing CHO system in respect of medium, environment and expression vector, modification of CHO cells themselves has drawn more and more attention. Here the main progress in CHO-modification is reviewed.