Adefovir has the lowest antiviral activity, but the incidence of resistance is lower than lamivudine and tibivudine, with 1.6% resistant at 2 years of treatment and 3% resistant at 3 years. However, this drug is cheaper and has a low resistance rate, so it is widely used in the clinic! In recent years, with the increase in the number of years of drug use, the clinical emergence of some drug-resistant patients, patients early manifestations of HBVDNA elevation, followed by liver function abnormalities. Clinical testing for resistance sites can be 236T, 180, or 181V or T. In some patients, the 181 variant is directly detected; after the initial administration of adefovir with elevated HBVDNA, is it necessary to switch to entecavir or to add lamivudine or telbivudine? At this time, it is necessary to test for resistance sites, and then select the medication according to the resistance sites, thus reducing the possibility of re-resistance or ineffective medication.