Pt co-catalyst WO3 (WO3/Pt) nanoparticle has been synthesized with a variation of platinum co-catalyst mass percentage using the microwave-assisted sol-gel method. The XRD characterization results show that WO3/Pt has a triclinic (anorthic) crystal structure. The touch diagram from UV-Vis DRS measurement exhibits that the energy band gap value of pristine WO3 nanoparticle of 2.89 eV, while for WO3/Pt was in the range of 3.23 -3.43 eV. PL spectra depicted the photoluminescence intensity decreasing by the addition of Pt. WO3/Pt improved photocatalytic properties in the degradation of methylene blue (MB) under visible light for 30 min irradiation up to 98.7% degraded.