To study the significance of T-lymphocytes rDNA transcription activity in diagnosis, differential diagnosis, therapeutical effect and evaluation of treatment for colorectal carcinoma, 59 cases of colorectal carcinoma, 20 cases of colorectal inflammatory disease and 9 volunteers were choosen to detect the T-lymphocyte rDNA transcription activity of peripheral blood T-lymphocyte by cell culture and CMIAS008 image analysis system of Ag-NOR. Results: T-lymphocytes rDNA transcription activity was decreased obviously in colorectal inflammatory patients. Compared with control group, both group showed markedly statistical difference (Ｐ＜0.01). Tlymphocytes rDNA transcription activity increased gradually to normal groups after operation and chemical treatment for colorectal carcinoma patients; but it decreased for recurrent patients three years after operation. Conclusions: The detection of T-lymphocytes transcription activity can be used as a differential criterion for colorectal carcinoma and colorectal inflammatory disease, meanwhile it also can be used as a reference criterion for evaluation of treatment and supervision of tumor recurrence.