The invention discloses a method for producing saponin and organic acid by using turmeric, which belongs to the field of biological engineering and solves the problem that the conventional method for extracting turmeric saponin by using a turmeric raw material has large discharge amounts of waste water and waste slag and cannot effectively use turmeric starch. The method comprises the steps of turmeric saponin release, turmeric starch saccharification, fermentation medium preparation, organic acid fermentation, saponin enrichment and saponin preparation. By pretreating the turmeric raw material by using fermentation and membrane separation coupling, the method has the advantages of pollution-free production of the saponin and the organic acid, high turmeric saponin extracting rate, full utilization of the turmeric starch, little waste water amount and little production during turmeric saponin production, pollution-free process and great industrial utilization value in the turmeric industry.