Objective To explore the clinical application of opportunistic screening(OS)for colorectal cancer in order to provide a basis for further improving the screening process and improving screening efficiency.Methods Clinical data of 3 398 patients with positive OS for colorectal cancer who completed total colonoscopy from January 2019 to December 2020 were retrospectively analyzed.After completion of the high risk factor questionnaire(HRFQ)and fecal immunochemical test(FIT),colonoscopy was recommended for patients who tested positive for either of the two screening methods.The age,sex,lesion detection and lesion location of the patients were counted,and the detection rate of colorectal tumors by different screening methods was compared according to the preliminary screening results.Results Among the 3 398 subjects,the detection rate of advanced adenoma and colorectal cancer in HRFQ(-)FIT(+)group were higher than that in HRFQ(+)FIT(-)group,there were significant differences between the two groups(P＜0.05).The detection rate of non-advanced adenoma in HRFQ(-)FIT(+)group was lower than that in HRFQ(+)FIT(+)group,there was significant difference between the two groups(P＜0.05).The sensitivity of FIT to colorectal tumors was generally better than that of HRFQ,and the sensitivity of FIT to distal colorectal tumors was higher than that of proximal colorectal tumors,there were significant differences between the two groups(P＜0.05).Conclusion The combination of HRFQ and FIT can screen more high-risk groups than FIT or HRFQ alone,thus detect more colorectal tumors,effectively improve the 5-year survival rate through timely endoscopic treatment or surgical resection,and ultimately reduce the morbidity and mortality of colorectal cancer in the population.