Colorectal cancer is the third most common malignancy worldwide and the second leading cause of cancer-related death. About 70% of colorectal cancers develop through the adenoma-cancer pathway. Early detection and resection of colorectal neoplastic lesions significantly reduce the morbidity and mortality of colorectal cancers. Colonoscopy is considered to be the preferred method for screening for colorectal lesions. However, as the number of endoscopic resection increases, the costs associated with pathological diagnosis of endoscopic resection and resection specimens increase year by year. In clinical practice, it will be very important and urgent to correctly judge the nature of colorectal lesions to avoid pathological diagnosis and then realize optical biopsy. Therefore, to clarify the endoscopic diagnosis of colorectal lesions, many endoscopic techniques have been applied clinically. Such as narrow-band imaging, magnifying narrow-band imaging endoscopy, magnifying chromoendoscopy and endocytoscopy. Endocytoscopy has two modes, EC-NBI mode and EC-staining mode. EC-NBI mode is to observe the microvessel on the mucosal surface of colorectal mucosa after switching the endoscopy to NBI mode. EC-V pattern is used to observe microvessels and then endoscopic diagnosis is performed. The EC-staining mode was that the cell nuclei and glandular duct morphology of colorectal lesions could be observed by endocytoscopy after chemical staining. Endocytoscopic diagnosis is performed clinically after observation of glandular ducts and nuclei. However, current studies on the diagnostic value of endoscopy in colorectal lesions are all retrospective studies with small samples, and there is a lack of clinical studies based on chinese population. Therefore, our center intends to conduct a study of a large sample to explore the diagnostic value of endoscopy in colorectal lesions.