Introduction. We investigated the proportion of myeloid-derived suppressor cells (MDSCs) and their subsets in patients with rheumatic diseases and clarified the association between these cells and the patient clinical data. Methods. Patients with rheumatic diseases and healthy controls were recruited. The clinical characteristics were obtained. The MDSCs and their subsets were marked with fluorescently labelled antibodies and were then analyzed with flow cytometry. Results. The patients included 31 with RA, 21 with AS, 14 with OA, 11 with SLE with arthritis, 13 with SLE without arthritis, 9 with Gout, 10 with HUA, and 25 healthy controls. The proportions of MDSCs, M-MDSCs, and G-MDSCs were higher in patients with RA than in healthy controls (6.56±6.77% versus 1.46±0.96%, 2.52±3.81% versus 0.35±0.35%, and 1.13±1.64% versus 0.18±0.14%; p<0.001). The same increased cells were also found in other patients. The proportions of MDSCs and M-MDSCs were mostly correlated with the patient's joint inflammation indexes and the disease activity. When other cell subsets were adjusted, the increased risk of arthritis was also obtained for M-MDSCs (adjusted OR=5.772; p=0.031). Conclusions. The expansion of MDSCs and their subsets was correlated with the disease activity and joint inflammation in patient with different rheumatic diseases. The proportion of M-MDSCs was associated with the risk of arthritis in those populations.