Mesenteric cyst,refers to a rare benign intra-abdominal lesion,with limited domestic and foreign researches on it with pregnancy.It is easy to be misdiagnosed because of its non-specific characteristics and lack of knowledge among clinicians.To explore the diagnosis and management of pregnancy complicated with abdominal mass,a misdiagnosis case of pregnancy complicated with giant mesenteric cyst was reported in this study,which summarized the clinical experience by analyzing the causes of misdiagnosis mainly from two aspects,ultrasound diagnosis and clinical thinking.In the diagnosis and treatment of pregnancy complicated with abdominal mass,clinicians should form a rigorous clinical thinking and make differential diagnosis based on the imaging data,so as to make a correct clinical diagnosis.