The viscoelastic properties of synthetic polyisoprenes(PI) reinforced by white carbon black(WCB) have been investigated and compared with WCB reinforced natural rubber(NR), including cure characteristics, physio-mechanical and dynamic mechanical properties. Compared with NR, PI loaded with the same amount of WCB(PI/WCB) exhibited shorter scorch time and optimal cure time, indicating that WCB fillers are comparatively easier to conjugate with PI. The tensile strength and elongation at break decreased with WCB filling in both PI and NR vulcanizates. The hardness of the rubber vulcanizates increased with the WCB filling in the rubber matrix. PI/WCB blends exhibited smaller hardness data, lower tensile strength, as well as lower elongation at break and tensile stress. Increasing the amount of WCB in rubber matrix induced the Payne effect. However, the Payne effect is much more obvious for the PI/WCB system, and PI/WCB also displayed higher storage modulus whereas lower loss modulus and loss tangent than NR/WCB, which could all be attributed to the poor dispersibilities of WCB in the PI matrix. The viscoelastic properties of synthetic polyisoprenes (PI) reinforced by white carbon black (WCB) have been investigated and compared with WCB reinforced natural rubber (NR), including cure characteristics, physio-mechanical and dynamic mechanical properties. Compared with NR, PI loaded with The same amount of WCB (PI / WCB) for shorter scorch time and optimal cure time, indicating that WCB fillers are comparatively easier to conjugate with PI. The tensile strength and elongation at break with WCB filling in both PI and NR vulcanizates. The hardness of the rubber vulcanizates increased with the WCB filling in the rubber matrix. PI / WCB blends exhibit smaller hardness data, lower tensile strength, as well as lower elongation at break and tensile stress. Increasing the amount of WCB in rubber matrix induced the Payne effect. However, the Payne effect is much more obvious for the PI / WCB system, and PI / WCB also displayed higher storage modulus but lower loss modulus and los s tangent than NR / WCB, which could all be attributed to the poor dispersibilities of WCB in the PI matrix.