Abstract: Objective To explore the levels of serum pyridinoline cross-linked carboxyterminal telopeptide of type Ⅰ collagen(ICTP), anti-cyclic citrullinated peptide(CCP)antibody and rheumatoid factors(RF)in patients with undifferentiated arthritis(UA). Methods Totally 60 UA patients were selected as UA group, and 32 healthy people with physical examination were selected as control group. The levels of serum ICTP, anti-CCP antibody and RF were compared between UA group and control group. The values of serum ICTP, anti-CCP antibody and RF levels in predicting the progression of UA to rheumatoid arthritis(RA)was analyzed. Results The levels of serum ICTP, anti-CCP antibody and RF in UA group were significantly higher than those in control group(P<0.05). Pearson correlation analysis showed that there was a significant positive correlation between serum ICTP and anti-CCP antibody(r=0.613, P<0.05), a significant positive correlation between serum ICTP and RF(r=0.438, P<0.05), and a significant positive correlation between serum anti-CCP antibody and RF(r=0.452, P<0.05). The results of Receiver Operating Characteristic - (ROC)curve analysis showed that the best cut-off values of ICTP, anti-CCP antibody and RF in predicting the progression of UA to RA were 4.52 μg/L, 20.84 U/mL and 18.50 U/mL respectively. The area under the curve(AUC)predicted by combination of serum ICTP, anti-CCP antibody and RF levels was significantly higher than that by RF(Z=2.573, P=0.010). Conclusion The levels of serum ICTP, anti-CCP antibody and RF have certain values in predicting the progression of UA to RA, and the combined detection of the three indexes shows great significance for the early prediction of the outcome of UA.