Objective To investigate the safety of intraoperative electron radiation therapy (IOERT) for stage Ⅰ hepatocellular carcinoma (HCC) by a cohort study.Methods From November 2010 to May 2012,16 patients who were pathologically diagnosed with stage Ⅰ HCC underwent IOERT after radical resection.With a cohort study,87 patients with stage Ⅰ HCC who underwent radical resection alone during the same period were qualified,and according to tumor size (＞ 5 cm and ≤ 5 cm) and resection margin (close margin and negative margin),32 of 87 patients made up the control group.The intraoperative and postoperative adverse events,liver function parameters,coagulogram,and routine blood parameters,as well as IOERT-related adverse reactions,were evaluated.Independent-samples t test was used for analyzing the differences between groups.Results Compared with the control group,the IOERT group had a significantly longer operative time ((275.4 ± 71.55) min vs.(184.7 ± 64.74) min,P =0.000),a slightly higher incidence of intraoperative adverse events (18.75％ vs.6.25％,P=1.000),a slightly lower incidence of operative complications (12.50％ vs.28.12％,P =0.460),and a lower perioperative mortality (0 vs.6％,P =0.440).Liver function parameters showed no significant differences between the two groups (P ＞ 0.05).There were no significant differences between the two groups in postoperative time to grade 1 or normal liver function parameters,median length of postoperative hospital stay,length of hospital stay in the surgical department,time to incision healing,and level of incision healing (P ＞ 0.05).During follow-up,no radiation hepatitis was found in the IOERT group.Conclusions As an adjuvant therapy after radical resection for early HCC,IOERT has no significant side effects on postoperative recovery and liver function,and an intraoperative dose of 15-16 Gy is safe.