Abstract: ［Abstract］Objective　To investigate the clinical value of blood β-hydroxybutyric acid and urine ketone in the diagnosis of diabetic ketosis. Methods　One hundred and fifteen patients with non-ketosis diabetics （NDK group）， 85 patients with diabetic ketosis（DK group）and 105 healthy people（control group）were enrolled in Chengmai People's Hospital from May 2012 to May 2014. Blood β-hydroxybutyric acid，urine ketone and blood glucose were detected; the correlation index of blood β-hydroxybutyric acid，urine ketone and blood glucose in NDK group and DK group were analyzed. The receiver operating characteristic curve（ROC）was performed in determining the diagnostic value of blood β-hydroxybutyric acid for diabetic ketosis. Results　The level of blood β-hydroxybutyric acid， positive rate of blood β-hydroxybutyric acid， urine ketone and level of blood glucose in DK group were higher than those in NDK group and NC group （P＜0.01）. Blood β-hydroxybutyric acid was positively correlated with urine ketone and blood glucose （r＝0.552，P＝0.000；r＝0.405，P＝0.010）. When urine ketone was used as diagnostic standard， the area under curve of blood β-hydroxybutyric acid was 0.839， the best cutoff value of β-hydroxybutyric acid was 0.64 mmol/L with the sensitivity was 81.6% and specificity was 89.2%. Conclusions Examinations of blood β-hydroxybutyric acid and urine ketone have great significance for the diagnosis of diabetic ketosis. The co-monitoring of blood β-hydroxybutyric acid and urine ketone can reduce the rates of missed diagnosis and misdiagnosis. The best cutoff value of β-hydroxybutyric acid to diagnose diabetic ketosis was 0.64 mmol/L.