Objective To explore the optimal cut-off value of catheter to vein ratio （CVR） in predicting symptomatic venous thromboembolism (VTE) related to peripherally inserted central catheter (PICC) in patients with hematologic malignancy. Methods A total of 273 patients with hematologic malignancy who had a PICC were studied. Symptomatic VTE was diagnosed based on patient′s clinical symptoms and Ultrasonic color Doppler. The optimal cut-off value of CVR was determined by logistic regression analysis and receiver operating characteristic （ROC） curve. Results The prevalence of symptomatic VTE was 6.23%.Compared with CVR less than or equal to 34%, CVR between 35% and 45%, ≥46% had odds ratios of 16.762 and 15.529 respectively.ROC analysis determined that a 38% CVR was the ideal cut off point. Conclusion There is a close relationship between CVR and risk of PICC symptomatic VTE, and CVR less than or equal to 38% is recommended.