Objective: To analyze the diagnosis effect of preoperative colonoscopy biopsy and surgical resection pathological specimens in colorectal high-grade intraepithelial neoplasia (high grade colorectal intraepithelial neoplasia, HGCIN). Methods: A total of 52 cases of patients with HGCIN in our hospital from April 2012 to April 2015 were selected. All patients received preoperative colonoscopy biopsy and clinical features of surgical pathology specimens. A retrospective analysis of two diagnostic methods was done, which summarized reasonable diagnostic methods of colorectal HGCIN and explored the difference between preoperative biopsy and surgical resection of pathological. Results: 52 cases of patients who underwent preoperative colonoscopy biopsies were diagnosed as HGCIN, 4 patients were diagnosed as HGCIN through surgical specimens pathological examination 7.7% (4/52) accord with preoperative diagnosis, the other 48 patients were diagnosed as adenocarcinoma, the comparison presence of preoperative biopsy and pathology test results statistically significant (P<0.05). Meanwhile, misdiagnosis rate of rectum lesions was about 97.2% (35/36), the misdiagnosis rate of location of lesions in the colon was about 81.3% (13/16), the misdiagnosis chances of rectal lesions were higher than colon, which was statistically significant (P<0.05). Conclusion: The difference of colorectal HGCIN surgery biopsy and surgical specimens pathological was apparent. To ensure patient a more reasonable clinical diagnosis and treatment of patients, rigorous assessing the severity of differentiation and other relevant circumstances, actively communicate with pathologist were needed.