Objective To explore the reasons of abnormal decannulation in patients with malignant tumor undergoing chemotherapy during peripherally inserted central catheter ( PICC ) period. Methods A prospective study was conducted among 291 cancer patients who used PICC for chemotherapy in Hunan Provincial People′s Hospital from January 2012 to June 2014. The occurrence of complications during PICC period and the reasons of abnormal decannulation in patients were investigated and collected. The time of follow-up was one year. Results Among 291 patients, there were 72 cases ( 24. 74%) of PICC complications and 44 cases (15.12%) of abnormal decannulation, among which, there were 12 cases (4.12%) of upper extremity deep venous thrombosis ( UEDVT ) , 5 cases ( 1. 72%) of central line associated bloodstream infections (CLABSI), with an infection rate of 0.95 per 1 000 catheter days, 9 cases (3.09%) of exit-site infection, with an infection rate of 1.46 per 1 000 catheter days, 11 cases (3.78%) of catheter prolapse and 7 cases (2.41%) of occlusion. Single factor analysis showed that, the history of deep venous thrombosis ( DVT) and the types of chemotherapeutics could influence the incidence rate of abnormal decannulation of patients with PICC. Conclusions The incidence rate of abnormal decannulation in patients with malignant tumor undergoing chemotherapy during PICC is 15%. UEDVT is the main reason of abnormal decannulation of PICC, and the chemotherapeutics infusion is independent risk factor of abnormal decannulation.