The present invention relates to a method for preparing a garlic-fermented composition and a garlic-fermented composition prepared by the method, and the purpose of the present invention is to provide a garlic-fermented composition which is easy to take, has no side effect, and improves excellent pharmacological and physiological efficacies of garlic. To achieve this, the method for preparing a garlic-fermented composition according to an aspect of the present invention, comprises: a first fermentation step of mixing garlic, water, and a ferment strain, followed by fermentation, thereby decomposing and converting sugars and proteins of the garlic； and a second fermentation step of additionally supplying a carbon source to a filtrate obtained through solid-liquid separation of the fermented product, followed by fermentation, thereby removing ammonia of the filtrate and decomposing and converting the additionally supplied carbon source.
