Objective：To summarize ultrasonographic manifestations of plasma cell mastitis in 213 cases and to analyze reasons of missed diagnosis and misdiagnosis. Methods：Ultrasonographic manifestations of 213 cases of plasma cell mastitis testifed by pathology and reasons of missed diagnosis and misdiagnosis were retrospectively studied. Results：Among 213 cases，209 cases were detected lesions by ultrasond，including 195 limited and single lesions and 14 ductal ectasia lesions. Forty-eight cases were diagnosed as plas－ma cell mastitis by ultrasond and diagnosis accuracy rate was 22.54%；40 cases were misdiagnosed，misdiagnosis rate was 18.78%；4 cases were missed diagnosed，missed diagnosis rate was 1.88%.Utrasonographic manifestations of 209 cases included：ductal ectasia in 14 cases，cyst in 22 cases，solid nodule in 110 cases and mixed cystic and solid nodule in 63 cases. Internal blood flow signals were detected in 146 cases，rich in 94 cases. Conclusions：Ultrasonographic manifestations of plasma cell mastitis are varied and complex and it is uneasy to make correct diagnosis. Careful observations of ultrasonographic manifestations combined with clinical features are required in order to improve the diagnosis accuracy.