The invention discloses a processing process of natural sausage casings. The processing process comprises the steps of cleaning primitive intestines, soaking, removing mucous layers and muscle layers from intestines, flushing by high-pressure water filling, checking by water filling, measuring the size, pickling, and discharging from a bucket and storing, wherein a physical repeated freeze-thaw method is combined with a chemical bioenzyme digestion method in the process of removing the mucous layers and the muscle layers from the intestines. The processing process is simple; due to the physical repeated freeze-thaw method, cell membranes can be effectively broken, cell contents are released, and the subsequent chemical bioenzyme digestion method can be conveniently carried out, so that cell membranes and organelle structures in tissues can be broken and cells can be separated from matrixes to generate a cell removal effect; the tissues in the intestines are flushed out by adopting the high-pressure water filling process; the process is favorable for quickly removing the tissues except for the casings to obtain light, thin and transparent casings with good color and luster; in addition, the large-scale modern production of the casings can be realized, and the industry development is promoted while the production efficiency is improved.