In view of the current research status of probiotic fermented dairy products， which are mixed animal strains for fermenting animal source dairy products， this paper uses oats as the main raw material to prepare pure oat milk， enzymatic hydrolysis， adding 20% milk and 7% sucrose and appropriate amount of emulsifier. The stabilizer is composed of a fermentation medium. The Lactobacillus casei 05-20， which is selected from the fermented dairy products and has high growth and fertility and high fermentation activity， is used as a test strain to study the single factors such as inoculum size， fermentation temperature and fermentation time. The effect of Lactobacillus casei pure fermented oat milk product quality， the response surface test was used to optimize the process conditions of Lactobacillus casei pure fermented oat milk product， analyzed and evaluated the quality of Lactobacillus casei pure fermented oat milk product， including： sensory， physical and chemical ingredients， probiotics and functional ingredients， food safety， storage stability. The results showed that the optimum conditions for the fermentation of oat milk by Lactobacillus casei were 5.0% inoculation， 37 ℃ fermentation temperature and 5.3 h fermentation time. The fermented milk was yellowish， fine and fine in texture， with rich aroma of oatmeal and fermented aroma， fermented milk live bacteria number reached 8.8×108 CFU/mL， titration acidity was 49.05 °T， protein content was 1.76 g/100 g， fat content was 0.75 g/100 g， essential amino acid content accounted for 55.92% of total amino acid content， unsaturated fatty acid content was about 79.20% of total fatty acid content， oat β-glucan content was （92.00 ± 1.29） μg/mL， total phenol content was （13.00 ± 0.38） μg/mL， anti-digestion mass fraction was （19.61±0.02）%， no therapeutic microorganisms and toxins were detected， and the shelf life was 24 days. It provides a theoretical basis for the industrial production of Lactobacillus casei fermentation with plant protein oats-based dairy products， it also provides a new way for new probiotics to ferment other vegetable protein dairy products.