The invention relates to a preparation method of cephalosporin C sodium salt and 7-aminocephalosporanic acid. The method comprises the following steps: separating a cephalosporin C filtrate from a fermentation liquid by a membrane filtration manner; then extracting cephalosporin C from the filtrate by using an organic solvent to obtain a cephalosporin C extraction solution; mixing the cephalosporin C extraction solution and sodium 2-ethylhexanoate, carrying out a salt formation reaction, performing standing stratification, and collecting a heavy phase; adding an anti-solvent into the heavy phase for crystallization to obtain cephalosporin C sodium salt; and then dissolving cephalosporin C sodium salt by using purified water to obtain an aqueous solution of cephalosporin C sodium salt, adding an immobilized cephalosporin C acylase, and performing enzymatic hydrolysis, crystallization, filtration, washing and drying on cephalosporin C sodium salt to obtain 7-amino-cephalosporanic acid. Cephalosporin C sodium salt and 7-aminocephalosporanic acid prepared by the method are significantly superior to a conventional process, the product is used for preparation of cephalosporin downstreamproducts, the obtained products have higher quality, and medication is safer.