The invention discloses a thermosetting resin composition, a prepreg and a laminated board. The thermosetting resin composition is prepared from the following components: (1) 40-60 parts by weight ofpolyphenylene ether, (2) 30-50 parts by weight of an active ester oligomer, and (3) 10-20 parts by weight of an organosilicon polymer, wherein the polyphenylene ether has epoxy groups at both ends, and the number average molecular weight of the polyphenylene ether is 3000-10000; the active ester oligomer is DCPD type active ester; the organosilicon polymer is epoxy functionalized polysiloxane. Thethermosetting resin composition has very good activity and wettability; the prepreg and the laminated board which are prepared from the thermosetting resin composition have the advantages of being good in dielectric property, heat resistance, flame retardance, toughness, processability, and the like.