The present invention relates to vinyl-based thermoplastic resin composition having excellent thermal stability, which comprises a metal complex agent, and a first vinyl-based monomer and a second vinyl-based monomer having different iron ion concentration from each other, a method for manufacturing thereof, and vinyl-based thermoplastic resin manufactured therefrom. The accompanying vinyl-based thermoplastic resin composition can enhance thermal stability, and the vinyl-based thermoplastic resin manufactured from the composition may have excellent thermal stability. Thus, it can be easily applied to industries requiring thereof, in particular, industries of vinyl-based thermoplastic resin and its mold processed goods.