Objective To study the effects of Lactobacillus casei ATCC334 on the secretion of inflammatory factors and joint destruction in collagen-induced arthritis (CIA) rats and explore the possible mechanism. Methods Female Wistar rats were randomly divided into normal control group, CIA group and ATCC334 group with 7 rats each. The CIA model was established by intradermal injection of bovine type 2 collagen into the tail root of rats in the CIA group and ATCC334 group. The rats in the control group and CIA group were intragastrically perfused with 500 μL normal saline every day, and simultaneously the rats in the ATCC334 group were intragastrically perfused with Lactobacillus casei ATCC334 solution [2×108 colony forming unit (CFU)/mL] for continuous 28 days. Arthritis index and increased hind paw volume were used to evaluate the severity of arthritis. HE staining was used to observe the joint lesions. Levels of tumor necrosis factor α (TNF-α), interleukin-6 (IL-6) and IL-17 in the serum of rats were detected by ELISA. Results Compared with the CIA group, the indices of arthritis index, increased posterior paw volume, joint lesions and TNF-α, IL-6 and IL-17 levels were significantly reduced in the serum of the ATCC334 group. Conclusion Lactobacillus casei ATCC334 can significantly reduce the secretion of inflammatory factors and joint bone damage in CIA rats.