The invention provides novel application of 4-hydroxy salicylamide in the field of pharmacy. The compound is an inhibitor of ribonucleotide reductase (RR), and can achieve the aims of inhibiting replication of HBV and treating hepatitis, in particular the hepatitis B by inhibiting activity of RR enzyme to block synthesis of dNTPs (deoxynucleotide triphosphates) required by hepatitis B virus (HBV)replication, achieve the aim of preventing and treating liver cancer by inhibiting the activity of RR of liver cancer cells, including the RR activity activated by HBV to inhibit proliferation of liver cancer cells, and achieve the aim of treating various tumors by inhibiting the RR. The 4-hydroxy salicylamide can be used for preventing and treating hepatitis B, liver cancer, oropharyngeal epithelioma, colorectal cancer, ovarian cancer, non-small cell lung cancer, chronic myeloid leukemia and other tumors, and has important application prospect.