A production method of propionic acid fermented by immobilized microorganisms is characterized by comprising the following steps: strain culture, immobilized Propionibacterium freundii, submerged fermentation in liquid, and propionic acid extraction process: (1) strain culture: the slant strain of Propionibacterium freundii in a test tube is used as the production strain, and the flask culture and the seed tank culture are expanded; (2) Immobilization of Propionibacterium fischeri: the cultured strain obtained by amplification is input into a continuous centrifuge through a sterile pipeline, and the thalli are collected by centrifugation, and then sterile water with the original seed fermentation liquid volume1/20 ~115 in a seed tank is added to make a bacterial suspension, and then the bacterial suspension volume1/8 ~ is added. Adding 4%-6% concentration of sterile sodium alginate solution, adding 1.5-2.5 times volume of bacterial suspension, then adding 3%-5% concentration of polyvinyl alcohol, adding 0.5- 1.5 times volume of bacterial suspension, and stirring 1-2 hours; Dropping into 2%-4% calcium chloride solution with 5- 10 times the volume of bacterial suspension by a continuous drip irrigation machine with aseptic input, standing at room temperature for 2-3 hours, releasing the calcium chloride solution, and aseptically inputting the immobilized bacteria into a liquid fermentation tank. (3) Submerged fermentation: liquid fermentation medium (g/L): peptone 2-4g, sucrose 5- 15g, yeast extract 2-4g, glycerol 5- 15ml, ammonium phosphate 2-6g, calcium carbonate 4-8g, ammonium nitrate 1-3g and sodium lactate. Control the temperature in the tank at 30-35℃ and the tank pressure at 0.0 1-0.02 MPa, continuously stir for 36-48 hours until the propionic acid content reaches 20-40g/L, then discharge the fermentation liquid, enter the extraction process, and replenish sterile new fermentation liquid in the fermentation tank, and the volume of the liquid fermentation liquid is 10-50 of the immobilized bacteria volume. (4) propionic acid extraction step: filtering the fermentation broth with the pore size of 1-2 micron to remove microbial cells and macromolecular impurities, wherein the filtering operation pressure is 0.02-0.03 MPa and the operating temperature is 25-30 DEG C; Adjust that ph value of the filtrate to 6.0-6.5, and then carrying out static adsorption with anion exchange resin, wherein the volume-weight ratio of the filtrate to the anion exchange resin is10:1-15:1,the stir speed is 20-50 rpm, and the adsorption temperature is 25-30 DEG C.. Removing the supernatant, eluting the resin, ultrafiltering and concentrating the eluent with an ultrafiltration membrane, and performing cross-flow filtration with an ultrafiltration membrane with a molecular weight of 5,000-6,000 daltons, wherein the ultrafiltration operation pressure is 0.2-0.6 MPa and the temperature is15-30 DEG C, and crystallizing to obtain colorless and transparent crystal powder, and the purity of propionic acid products is more than or equal to 95%. Tianjin University of Science and Technology

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