Objective To explore the diagnostic value of acetic acid indigocarmine mixture(AIM)sandwich staining combined with flexile spectral imaging color enhancement(FICE)technology for colonoscopic Pit pattern classification for colorectal lesions.Methods 100 patients with colorectal lesions from June 2022 to October 2023 were selected as the research subjects,and 222 lesions;Patients were examined using conventional endoscopy,FICE,AIM sandwich staining+FICE,and the detection status and pathological type of Pit pattern classification were recorded.Calculate the sensitivity,specificity,positive predictive value(PPV),negative predictive value(NPV),and accuracy of Pit pattern classification diagnosis under different modes.Kappa was used to evaluate the consistency between Pit pattern classification and pathological examination under different modes.Evaluate diagnostic effectiveness using receiver operator characteristic curve(ROC curve).Results Compared with ordinary endoscopy(74.32％),FICE technology(92.34％)and AIM staining+FICE(97.30％)detected more lesions that matched the pathological results through Pit pattern classification,and AIM sandwich staining+FICE detected more than FICE,the differences were statistically significant(P＜0.05).Compared with ordinary endoscopy,the diagnostic accuracy of FICE and AIM staining+FICE for colorectal carcinoma lesions were higher,and AIM sandwich staining+FICE higher than FICE,the differences were statistically significant(P＜0.05).Compared with ordinary endoscopy,the diagnostic accuracy of FICE and AIM sandwich staining+FICE for early colorectal cancer were higher,the differences were statistically significant(P＜0.05).The area under the curve(AUC)predicted by ordinary endoscopy,FICE and AIM sandwich staining+FICE for colorectal carcinoma lesions were 0.815(95％CI:0.711～0.859),0.881(95％CI:0.752～0.904),and 0.933(95％CI:0.793～0.961),respectively;The AUC predicted by ordinary endoscopy,FICE and AIM sandwich staining+FICE for early colorectal cancer were 0.850(95％CI:0.720～0.866),0.938(95％CI:0.764～0.951),and 0.947(95％CI:0.803～0.972),respectively.For predicting colorectal carcinoma lesions and early colorectal cancer,the Youden index of AIM staining+FICE technology was the highest,with values of 0.955 and 0.968,respectively.Conclusion Under AIM sandwich staining+FICE,Pit pattern classification can detect more carcinoma lesions and early colorectal cancer,with high diagnostic accuracy and effective improvement of endoscopic diagnosis and treatment quality.