Taking autoimmune inflammation of rheumatoid arthritis as entry point, this paper discussed the clinical effect of horsetail mixture on rheumatoid arthritis (RA) and its mechanism. A total of 60 cases of patients with RA were randomly divided into experimental group and control group using randomized controlled trial. We observed its biochemistry, TNF-α and IL-10 before and after treatment, and then systematically assessed the clinical effect of horsetail on RA. Results showed that the total effective rate of experimental group was 80%, while that of control group was 16.67%. After statistical treatment, the differences between two groups were significant (p<0.01). Comparison of the difference value of TNF-α (p<0.05) and IL-0.05 in serum between groups before and after treatment, there were significant differences. Comparison of CRP within group before and after treatment was significantly different (p<0.05), while comparison of CRP between groups was not significantly different (p>0.05). Comparison of ESR and RF within group before and after treatment was significantly different (p<0.01), and comparison of them between groups was also significantly different (p<0.05). Comparison of difference values within group before and after treatment were also significantly different (p<0.01). It was concluded that horsetail mixture has remarkable curative effect on rheumatoid arthritis, and its clinical application is safe and reliable. It has obvious down regulatory effect on cell factor TNF-α related to RA, that is, it can down regulate the level of pre-inflammatory factor TNF-α as well as the level of anti-inflammatory factor IL-10. Therefore, it is considered that the regulating effect of horsetail mixture on TNF-α and IL-10 is one of the mechanisms of its treatment on RA.