Abstract: Objective:To explore the clinical features and serological characteristics of patients with undifferentiated connective tissue diseases(UCTD) so as to elevate the cognition of UCTD.Methods:The clinical features,laboratory data and management of 92 patients with UCTD were analyzed retrospectively.Results:The most common clinical manifestations were the joint disease(67 cases),fever(30 cases),Raynauds phenomenon(25 cases),decreased white blood cell count(13 cases),interstitial lung disease(8 cases),and dry mouth and/or dry eye(7 cases).The positive rate of serum anti-nuclear antibody reached 100%,among which anti u1RNP antibodies accounted for 29 cases,anti-SSA/RO60 21 cases,anti-SSA/RO52 16 cases,elevated immunoglobulin 23 cases and decreased complement C3 17 cases.Conclusions:The clinical and serological manifestations of UCTD are moderate simplified connective tissue diseases.Excepting for the interstitial lung disease,the symptoms of other diseases are generally mild and the prognosis is good.The conversion of the patients needs further follow-up.