Hepatitis C virus (HCV) infection is easy to chronic and can progress to cirrhosis and liver cancer. Direct-acting antiviral treatment can significantly improve the prognosis of the disease and the efficacy is seemingly not affected by a variety of viral factors. In addition, direct-acting antiviral agents therapy may affect the transformation of the immune cells and ameliorate the host immune status consequently. This study mainly investigated the relationship between Direct Acting Antiviral Treatment effect and the functional activity of myeloid-derived suppressor cells (MDSCs) and natural killer cells (NK cells) in Chronic Hepatitis C.