Background:Hepatocellular carcinoma (HCC) survivors are increasing due to the improvement of survival. Follow-up scheme to prevent recurrence is routinely recommended, but are these patients exposed to increased risks of second malignancies remains unknown. We aimed to identify risk factors for second primary malignancies (SPM) among HCC survivors and develop a predicting model accordingly. Methods: We identified HCC patients in the Surveillance, Epidemiology, and End Results (SEER) database from 2004 to 2014. For the incidence of specific SPMs, standardized incidence ratios (SIRs) were calculated. The proportional hazard model was performed in order to discover hazards of SPM, and a competing-risk nomogram was developed to stratify patients with different incidences for SPM. Results:The crude incidence of SPM was 2.70% in HCC survivors, with the SIR of 1.09. HCC survivors had significantly higher incidences of SPM in the following sites: oral cavity and pharynx, stomach, intra and extrahepatic bile duct, lung and bronchus, kidney and renal pelvis, thyroid and lymphatic system (p< 0.05). Patients with diagnosed age at 61-75 years old, smaller tumor size, better histologic differentiation, earlier AJCC stage or surgical history had higher risks for SPM. The c-index of the competing-risk nomogram was 0.663. The cumulative incidences of SPM were significantly different among each quartile of patients stratified by the predicting model (p< 0.05). Conclusion:HCC survivors had an excess risk for SPMs, especially those with promising prognostic factors. This nomogram was the first competing-risk model for identifying high-risk cohort and assist clinical screening.