The disclosure provides a method for treating hepatitis B, including: administering an effective amount of proanthocyanidins wherein the formula of a monomer of the proanthocyanidins is shown as Formula (I):wherein R1 is OCH3, R2 is OH and R3 is H, or R1 is OH and R2 and R3 both are H, or R1 and R2 both are OH and R3 is H, or R1, R2 and R3 all are OH, and R4 is 3-(α)-OH, 3-(β)-OH, 3-(α)-O-sugar or 3-(β)-O-sugar. Bonding between adjacent monomers take place at C4, C8 Carbon-carbon bond or C2, C7 oxygen bond of A type or C4, C8 or C4, C6 Carbon-carbon bond of B type or C type of proanthocyanidins. And the polymerized number is from 2 to 30.
