The invention discloses a preparation method for separating a biochemical medicament from small sheep intestine mucosas, in particular a preparation method for producing sodium heparin by using small sheep intestines. The preparation method for producing the sodium heparin by using the small sheep intestines is characterized by comprising the following steps of: preparation of intestine mucosas, enzymolysis, adsorption, elution, precipitation, desalting, dehydration and drying to obtain the sodium heparin. Therefore, the method has the advantages of high yield, low sodium heparin activity loss, stable quality and capability of solving the problem of stink in a sodium heparin workshop by adopting a workshop waste gas purification treatment device; 10,000 to 12,000 small sheep intestine mucosas are needed for producing 100 million units of sodium heparin by using the conventional process, and 6,000 to 8,000 small sheep intestine mucosas are needed for producing 100 million units of sodium heparin by using the preparation method of the invention; and the valence and activity of the sodium heparin are greatly improved so that the production cost is greatly reduced, and the profit is improved by over 40 percent.