The Chinese hamster ovary (CHO) cell is a fibroblast-like cell that produces proteins with post-translational modifications similar to human glycosylation. It is widely used in the production of recombinant therapeutic proteins and monoclonal antibodies. Culturing CHO cells typically requires the addition of a certain proportion of fetal bovine serum (FBS) to maintain cell proliferation and passaging. However, serum is characterized by its complex composition, batch-to-batch variability, high cost, and potential risk of exogenous contaminants such as mycoplasma and viruses, which impact the purity and safety of the synthesized proteins. Therefore, search for serum alternatives and development of serum-free media for CHO-based protein biomanufacturing are of great significance. This review systematically summarizes the application advantages of CHO cells and strategies for high-density expression. It highlights the developmental trends of serum substitutes from human platelet lysates to animal-free extracts and microbial-derived substances and elucidates the mechanisms by which these substitutes enhance CHO cell culture performance and recombinant protein production, aiming to provide theoretical guidance for exploring novel serum alternatives and developing serum-free media for CHO cells.