Transition metal phosphides are ideal inexpensive electrocatalysts for water-splitting, but the catalytic activity still falls behind that of noble metal catalysts. Therefore, developing valid strategies to boost the electrocatalytic activity is urgent to promote large-scale applications. Herein, a microwave combustion strategy (20 s) is applied to synthesize N-doped CoP/Ni2P heterojunctions (N-CoP/Ni2P) with porous structure. The porous structure expands the specific surface area and accelerates the mass transport efficiency. Importantly, the pyrrolic N/pyridinic N content is adjusted by changing the amount of urea during the synthesis process and then optimizing the adsorption/desorption capacity for H*/OH* to enhance the catalyst activity. Then, the synthesized N-CoP/Ni2P exhibits small overpotentials of 111 and 133 mV for HER in acidic and alkaline electrolytes and 290 mV for OER in alkaline electrolytes. This work provides an original and efficient approach to the synthesis of porous metal phosphides.