In this work, we construct a well-designed integrated photocatalyst with massive specific surface area of active sites for high-efficiency photocatalytic splitting water. Taking CdS/Co2P as a case, we first put forward a typical one-step hydrothermal strategy to synthesize cobalt phosphide (Co2P) microspheres within 3 h and obtain one-dimensional cadmium sulfide (CdS) nanowires deposition on Co2P microspheres at room temperature. Under optimal conditions, 50 mg photocatalyst nanocomposite can show the highest rate for H2 evolution was 723 μmol h−1 which is about 360 times greater than that of pure Co2P microspheres under visible light, and the highest quantum efficiency (QE) of 23.6% is achieved at 470 nm. The system shows extraordinarily high activity and great stability. Meanwhile, the photocatalytic hydrogen evolution mechanism of photocatalyst nanocomposites is also proposed and discussed. To our knowledge, it has been rarely reported that a green and rapid one-step hydrothermal synthesis route for pure phase metal phosphide and applying photocatalyst based on an earth-abundant ideal metal phosphide in photocatalytic hydrogen evolution to date.