The invention discloses a foaming type structural adhesive and a preparation method thereof. The foaming type structural adhesive comprises the following raw materials in percentage by weight: 20-50%of epoxy resin, 10-35% of a toughening agent, 2-15% of thermoplastic resin, 10-25% of filler, 1-15% of a foaming agent, 1-10% of a foaming accelerator, 1-10% of a curing agent and 0.5-5% of an accelerator. Wherein the epoxy resin comprises at least one of bisphenol A glycidyl ether, bisphenol F glycidyl ether and bisphenol A / F diglycidyl ether; wherein the toughening agent is selected from at least one of a core-shell polymer dispersed in epoxy resin, a carboxyl-terminated butadiene rubber epoxy adduct, polyurethane-modified epoxy resin, polyether amine-modified epoxy resin and an adduct of dimer fatty acid and epoxy resin; wherein the thermoplastic resin is selected from at least one of solid rubber, phenoxy resin, thermoplastic polyether and thermoplastic polyurethane. After the foamed structural adhesive is cured, good bonding strength is provided for a bonding layer, and a connecting gap between metal plates can be effectively compensated.