The present invention relates to a thermosetting resin composition and application thereof, said thermosetting resin composition comprising: A: a styrene-butadiene-styrene triblock copolymer having a star-shaped structure; B: a linear olefin resin containing 1,2-ethylene, and a modifier thereof, C: at least one resin or small molecule compound substituted with an acrylic group; taking the total mass of component A, component B, and component C as 100%, the added amount of said component A is 3%-85%, the added amount of said component B is 10%-95%, and the added amount of said component C is 1%-70%. The resin composition provided by the present invention does not undergo phase separation under initiator conditions, and has high heat resistance and a relatively low dielectric constant and dielectric loss tangent value, and is capable of providing the desired dielectric properties and thermal reliability of a copper-clad plate.