The invention discloses a water-based all-purpose adhesive and a preparation method thereof. The water-based all-purpose adhesive comprises the following components: a multi-component copolymerized acrylic emulsion, a VAE emulsion, a rosin emulsion, a polyurethane emulsion, a defoaming agent, a wetting agent, a thickening agent and a flame retardant. The preparation method comprises the following steps: firstly, adding 35% of polybasic copolymerized acrylic emulsion into a stirring kettle, and stirring; then adding 25% VAE emulsion into the stirring kettle, and continuously stirring; adding 25% of rosin emulsion into the stirring kettle, and continuously stirring; adding 15% of polyurethane emulsion into the stirring kettle, and continuously stirring; finally, 0.2% of the defoaming agent prepared in advance is added according to the total amount and continuously stirred, then 0.15% of the wetting agent is added and continuously stirred, then 0.3% of the thickening agent is added and stirred to be completely and uniformly mixed, finally 0.15% of the flame retardant is added and uniformly stirred, and the coating can be obtained. The coating has almost zero emission of VOC, is non-toxic, non-combustible and non-explosive and is easy to construct.