In this paper, Pt nanoclusters are firstly decorated on the surface of two dimensional (2D) g-C3N4 nanosheets. Furthermore, 1D CdS nanowires are introduced to form the heterojunction of g-C3N4/CdS. The as-prepared Pt/g-C3N4/CdS shows 7.4 times improved electrocatalytic performance on methanol oxidation under visible light (> 420 nm) irradiation compare to dark condition. Moreover, the stability of corresponding electrode is significantly improved by evaluating on chronoamperometric and chronopotentiometry curves. The synergistic effects of photo-and electro-catalysis together with the efficient charger separation in the heterojunction of g-C3N4/CdS contribute to the above improvements. The present studies provide an effective pathway to design a heterojunction as the photo-activated support in the application of direct methanol fuel cell.