The present invention relates to betaine or a composition comprising the same for accelerating liver regeneration, more particularly, a therapeutic pharmaceutical composition comprising betaine represented by formula 1 as an active ingredient for promoting the recovery of injured or resected liver to the normal liver. The most effective treatment for chronic liver disease, particularly in the terminal stage, is hepatectomy and liver transplantation. In Living Donor Liver Transplantation (LDLT) that has been increasing since 1990, rapid regeneration of liver tissues is essential for both donor and recipient to inhibit complications and thus for the success of the treatment. Betaine accelerates the recovery and growth of injured liver to the normal liver, so that it can be effectively used for the successful LDLT or therapeutic hepatectomy.