Abstract: Objective To observe the efficacy， safety and doseresponse relationship of novaferon in treatment of metastatic colorectal cancer patients who had received at least two prior palliative regimens， and assess the effects on the immune function of subjects. Methods One hundred and five patients were enrolled from May 2011 to December 2012. According to the different treatment modalities and ultimately maintain therapeutic dose， the subjects were divided into three groups： the placebogroup（15 cases, saline），the lowdose treatment group（69 cases, novaferon ＜40μg each time, 3 times a week） and the highdose treatment group（21 cases, novaferon 40μg each time, 3 times a week）. The proportions of NK and CD4+CD25high Foxp3+Treg cells in the peripheral blood samples were detected from 57 subjects by flow cytometry before and after treatment. Then， the changes of NK and Treg cells were analyzed. Results After 6 weeks of treatment， disease control rate（DCR） of the highdose treatment group was 47.4%, higher than 21.4% of the placebo group. The difference was statistically significant（P＜0.05）. The major adverse reactions of novaferon were “flulike” symptoms， bone marrow suppression， abnormal liver function and gastrointestinal discomfort. After treatment， the NK cells in the highdose treatment group had increased significantly， Treg cells decreased significantly compared with baseline（P＜0.05）. Conclusion Novaferon has moderate efficacy and less adverse reactions in treatment of metastatic colorectal cancer. Furthermore, it can improve the immune function and life quality of patients.