The invention provides a preparation method of novel biological epoxy resin containing a pyridazinone structure, and belongs to the technical field of material science. The preparation method comprises the following steps of preparing intermediate acid by using guaiacol and succinic anhydride as bio-based raw materials through a Friedel-crafts reaction under the action of Lewis acid serving as a catalyst; performing a ring-closure reaction on the intermediate acid under the action of hydrazine hydrate to obtain a nitrogen-containing heterocyclic compound; dehydrogenizing by taking sodium 3-nitrobenzene sulfonate as an oxidizing agent to obtain a bisphenol-like compound containing the pyridazinone structure; lastly, introducing epoxide groups to the two ends of the compound containing the pyridazinone structure by taking epichlorohydrin as a reagent. Ring opening of an epoxy group in bisphenol A diglycidyl ether is initiated by taking compounds GSA, GSHZ and GSPZ as bio-based curing agents, so as to form a three-dimensional network structure for curing by crosslinking. In the preparation method, the epoxy resin containing the pyridazinone structure and a curing agent thereof are obtained from the bio-based raw materials, and the cured resin has high thermal stability and a wide application prospect in the fields of coatings, adhesives and aerospace.