Abstract: Objective: To evaluate the diagnostic value of color Doppler uhrasonography (CDUS) in nutcracker syndrome by receiver operating characteristic curve (ROC curve).Methods: The left renal vein (LRV) was measured on horizontal decubitus in 43 patients and 23 control subjects by CDUS.The interior diameter (D₁) and flow velocit (V₁) of LRV between superior mesenteric artery (SMA) and abdominal artery (AA),the interior diameter (D₂) and flow velocit (V₂) of LRV near the left of AA were recorded and analyzed in order to diferentiate nutcracker syndrome and controls.Repeated measuring the parameters above after 15 minutes keeping back after the extension bit.ROC curve of CDUS diagnosing nutcracker syndrome were drawn.The areas under curves (AUC) and diagnosis cut-off points of parameters in nutcracker syndrome were calculated.Results: D₂/D₁ and V₁/V₂ in patients with nutcracker syndrome were higher significantly than those in normal control subjects (P<0.05),the AUC of D₂/D₁ and V₁/V₂ were 0.966 and 0.969,respectively.The diagnosis cut-off point of D₂/D₁ and V₁/V₂ was 3.1 and 4.3,respectively.Conclusions: CDUS is an effective diagnosis method for nutcracker syndrome.