Objectives To study the clinical significance of the early diagnosis on colorectal cancer and the value of monitoring precancerous lesions of p53 gene examination. Methods Histological specimens of tumor from 110 patients with colorectal neoplasms were collected under the endoscopy, another 10 normal intestinal mucosa tissues with benign enteropathy as a control group. By PCR-SSCP methods, examined p53 exon 5～8 of mutation circumstance, made pathological section at the same time, and combine to track the observation. Results 24 patients p53 gene mutation were detected out in 78 cases colorectal cancers,counted up 32 4%, among 17 patients were moderate,low differentiation, 3 patients of them were mucinous adenocarcinoma.There are 6 patients p53 gene mutation in 36 cases colorectal adenoma,counted up 16 7%, among them an patient of Ⅱ～Ⅲ class atypical hyperplasia adenoma occurrence canceration in the next 10 months.There was no p53 gene mutation in normal intestinal mucosa tissue.Conclusions p53 gene examination combinated with pathological examination could monitor precancerous lesions and early diagnosis of the colorectal cancer.