A viscosity-reducing polycarboxylate superplasticizer (VR-PCE-TR) with narrow molecular distribution was synthesized by thermally initiated reversible addition-fragmentation chain transfer (RAFT) polymerization in continuous tubular reactor, using isoprenyl-PE-PPG and maleic anhydride as main raw materials. The molecular structure of VR-PCE-TR was determined by 1H NMR、FTIR and GPC. Then, the surface tension, uniformity, concrete experiment and mechanical strength have been measured to compare working performance and rheological properties with various viscosity-reducing polycarboxylate superplasticizers, which are synthesized by conventional free radical polymerization. The results show that when the mass fraction of polycarboxylate superplasticizer is 10%, VR-PCE-TR has a lower surface tension (30.65 mN/m); When polycarboxylate superplasticizers content are 8 mg/g, the cement slurry with VR-PCE-TR has a higher adsorption capacity (2.803 mg/g); When the dosage of polycarboxylate superplasticizers are 0.13%, the cement slurry with VR-PCE-TR has better dispersion and dispersion retention performance; When the dosage of polycarboxylate superplasticizers are 0.4%, the cement slurry with VR-PCE-TR has a lower yield stress (1.3 Pa) and lower plastic viscosity (0.26 Pa·s).Furthermore, the synthesis of VR-PCE-TR by thermally initiated RAFT polymerization in continuous tubular reactor without degassing process, are able to maintain the polymerization speed and control, achieving narrower molecular distribution (PDI=1.19), better viscosity reduction effect and application performance.