Objective :To study mutation of Ps3 gene and its relationship with histologic grade and Dukes' stage in colorectal cancer. Methods :PCR-SSCP was used to detect mutations of Ps3 in 30 colorectal cancer patients. Results: It was found that 6 mutations (20. 0%) in the coding region of P53 gene. One mutation was located in exon4; 5 mutations were located in exon 5; none of mutation was found in exon 2 and 3. According to the histologic grade of of colorectal cancer,the frequencies of P53 gene mutation were 1/8 (12. 5%) in the well differentiated and in the moderately differentiated as well,3/10 (30. 0%) in the poorly differenctiated and 1/4 (25.0%) in the undifferentiated. In clinic, the frequencies of P53 gene mutation were associated with Dukes stage: 1/10 (10. 0 % ) in B stage, 2/12 (16. 7%) in C Stage,3/8(37. 5%) in D stage. Conclusion:The mutation of P53 gene is related to Dukes＇ stage,and the P53 gene mutation hardly occurs in exon 2,3 in coloretal cancer.