Abstract: The patient arrived at our hospital with a complaint of diarrhea and narrow stools. His colonoscopy couldn't pass through the sigmoid because of the obstruction of tumor, but CT and barium enema indi-cated another upper tumor. Checking the colon and rectum during operation confirmed the tumor of splenic flexure. The pathological diagnosis of 2 tumors was malignant. Final diagnosis was Synchronous Carcinoma (SC). Missed diagnosis or misdiagnosis of multiple primary colorectal carcinoma is not rare,the combination of enough pre-operative examination, overall operative exploration and post-operative follow-up is necessary. The standardized curative therapy is also important.