Background: With the expanding population of colorectal cancer (CRC) survivors in the United States, more attention began to he focused on the second primary malignancy in these CRC survivors.The present study attempts to identify the incidence characteristics of second primary malignancy after diagnosis of primary colon and rectal cancer.Methods: 189,890 colon cancer (CC) and 83,802 rectal cancer (RC) cases were identified from Surveillance,Epidemiology and End Results Program (SEER) database.Expected incidence rates were stratified by age, race,stage, calendar year of first CRC diagnosis and latency period since first CRC diagnosis.The standardized incidence ratio (SIR) and excess risk (ER), measures for estimating risk of second primary malignancy, were respectively calculated for CC and RC.Results: Both CC and RC survivors had higher risk of developing second primary malignancy, and CC was higher than RC (SIRCC=1.13;SIRRC=1.05).The risks of cancer of small intestine (SIR=4.03), colon (SIR=1.79)and rectum (SIR=1.80) were the highest in CC patients, and the risk of cancer of rectum (SIR=2.88), small intestine (SIR=2.16) and colon (SIR=1.39) were greatest in RC patients.According to stratified analyses, we also identified the incidence characteristics which contribute to high risk of developing a second primary malignancy, including age between 20 and 40, American Indian/Alaska Native, localized stage, diagnosed at calendar year from 2002 to 2012 and the latency between 12 and 59 months.Conclusion: Both CC and RC survivors remain at higher risk of second primary malignancy.The identification of incidence characteristics of second primary malignancy is extremely essential for continuous cancer surveillance among CRC survivors.