The present invention relates to an oral insulin enteric-coated capsule and the preparation method, the raw materials use the insulin powder: each capsule has 10 units; excipients adopt medical starch: each capsule has 0.09g of starch granules and 0.01g of starch, the capsule adopts the common enteric-coated capsule, the medical starch is placed in a mixer, the starch paste is prepared into the soft material, a 20 mesh nylon screen is used for granulation, a 18 mesh screen is used for size stabilization after drying, then the starch is transferred into a mixing department for cooling, fine powder is screened out, and the remaining starch granules are ready for use; 2. the screened fine powder and the insulin fine powder are mixed fully and mixed evenly according to the incremental method and then are fully mixed with the starch granules which are produced in step 1; 3. the powder is transferred to a capsule filling department, an automatic capsule filling machine is used for filling; 4. the capsule after the filling is transferred to an aluminum foil packaging department for packaging after the polishing; 5. the capsule is transferred into a packaging room for packaging after the aluminum foil and then is transferred to a refrigerator chamber after completion. The present invention applies the oral insulin enteric-coated capsule for treating diabetes, the cost is low, the efficacy is good, the administration is easy, and the patients can avoid the suffering of the injection.