The invention relates to a gelatin preparation process for acid process bone element gelatin. The process is characterized in that animal bones are sequentially subjected to steps of crushing, degreasing, acid soaking, ash soaking, water washing, gelatin extraction, purification, concentration, sterilization, forming and drying to obtain the bone element gelatin; the ash soaking step comprises the processes that bone particles obtained after the acid soaking are soaked for 15 to 20 hours in lime emulsion with the concentration being 3 to 8 baume degree, then, the lime emulsion is completely discharged, 35-percent phosphoric acid water solution is added for treatment for 3 to 5 hours, and 5L of phosphoric acid water solution is added for each ton of bone grains. Through the optimized control and innovation on the gelatin preparation process, the material selection and the parameters, the technical problems of poor product performance stability and low yield in the gelatin preparation process for the acid process bone element gelatin are solved, the production period is shortened to 3 to 5 days, the waste water discharge quantity is low, the cost is low, in addition, the yield is as high as more than 90 percent, and good foundation is laid for the industrial scale production.