Lamivudine is most widely used in China. Lamivudine is an orally administered nucleoside analogue, chemically known as 2′,3′-dideoxy-3-thiocytosine, or 3TC, which was first used in the antiviral treatment of AIDS because of its inhibitory effect on the activity of reverse transcriptase. The mechanism of action of 3TC to inhibit HBV replication is that after phosphorylation in the cell, the drug can compete with dCTP to enter the synthesized DNA strand because it is similar to deoxycytidine nucleoside (dCTP), thus preventing the DNA from continuing to extend and terminating replication. This replication termination effect is effective for both negative and positive strands of HBV DNA. The mechanism of drug resistance is due to a point mutation in the polymutase gene region. The sub-structural domain of the C region of the multimerase, the active site of HBV reverse transcription, consists of tyrosine (Y)-methionine (M)-aspartate (D)-aspartate (D), or YMDD, which is the binding site for 3TC interference with HBV replication. When the methionine at position 552 in YMDD can be replaced by valine (V) or isoleucine (I), YV552DD or YI552DD is generated, resulting in a change in the spatial configuration of the substructural domain, which prevents binding to 3TC.