The invention discloses a method for preparing GABA beverage employing lactobacillus fermentation on agrocybe cylindracea, and belongs to the technical field of functional beverage processing methods. The method comprises the following processing steps: (1) separating and screening lactobacillus; (2) screening agrocybe cylindracea; (3) preparing agrocybe cylindracea homogenate; (4) carrying out lactobacillus fermentation to obtain a GABA fermentation liquor; and (5) preparing the GABA agrocybe cylindracea beverage from the agrocybe cylindracea homogenate and the GABA fermentation liquor. The lactobacillus GABA beverage obtained by the method is stable in property, free of harm to environment, convenient to use, and suitable for various people for eating, and large-scale industrialized production.