Objective:To find the distribution of nanobacteria in synovial fluid of rheumatoid arthritis patients and healthy people,so as to analyze the status of infection with nanobacteria in rheumatoid arthritis.Methods: 1.Nanobacteria was identified by PCR in synovial fluid samples from 30 rheumatoid arthritis patients and 30 healthy people.2.Nanobacteria was cultured from synovial fluid samples of 30 rheumatoid arthritis patients and 30 healthy people,and identified by indirect mmunofluorescence staining.Results: The positive rate of nanobacteria was 3.3% and 33.3 % for the synovial fluid samples of 30 healthy people and 30 rheumatoid arthritis patients,respectively,there was significant difference(χ2=9.017,P=0.0030.05).The positive rate of nanobacteria was 3.3% and 30.0 % for the synovial fluid samples of 30 healthy people and 30 rheumatoid arthritis patients,respectively by PCR.Conclusion: There was nanobacteria in synovial fluid of patients with rheumatoid arthritis.The infection of the nanobacteria may result in rheumatoid arthritis.PCR can be widely used for the rapid detection of nanobacteria infection in rheumatoid arthritis.