Thermoplastic vulcanizates (TPVs) based on high-impact polystyrene (HIPS)/styrene–butadiene rubber (SBR) blends were prepared by dynamic vulcanization technique, and the TPVs were compatibilized by styrene–butadiene–styrene block copolymer (SBS). Experimental results indicate that SBS had a good compatibilization effect on the HIPS/SBR TPVs. A rubber process analyzer reveals that elastic modulus increased with increasing frequency and increasing SBR content in the TPVs led to obvious decrease in elastic modulus. A softening phenomenon could be observed in the stress–stretch curves of HIPS/SBR and HIPS/SBS/SBR TPVs during the uniaxial loading–unloading cycles. Compatibilized HIPS/SBR TPV had the relatively lower stress and internal friction loss.