The invention discloses an in-situ compatibilization polymerization enhanced thermosetting phenolic foam insulation board and a preparation method thereof, wherein the in-situ compatibilization polymerization enhanced thermosetting phenolic foam insulation board comprises the following materials in parts by weight: 50-60 parts of resol, 20-30 parts of hydroxymethyl polyamide resin, 20-35 parts of a modified filler, 5-10 parts of a curing agent, 3-7 parts of an emulgator, 8-15 parts of a foaming agent, 0.5-1 part of a heat stabilizer, and 0.5-1 part of an ultraviolet light absorber; the resol is a component of foamex, the hydroxymethyl polyamide resin is a chain extender and a toughening component, and the modified filler is an in-situ compatibilization polymerization enhancing component. The resol, the hydroxymethyl polyamide resin, the modified filler, the curing agent, the emulgator, the foaming agent, the heat stabilizer and the ultraviolet light absorber prepared in advance are added into a reaction kettle, stirred evenly, and applied onto a non-woven fabric; on a continuous board production line, the temperature is kept at 70-75 DEG C, and crosslinking and foaming are performed within 20 minutes to obtain the in-situ compatibilization polymerization enhanced thermosetting phenolic foam insulation board. The in-situ compatibilization polymerization enhanced thermosetting phenolic foam insulation board is low in residue rate, high in compression strength and tensile strength, and good in heat resistance and ageing resistance.