In this study, a general and effective phosphorization strategy is successfully demonstrated to enhance supercapacitor performance of various transition metals oxide or hydroxide, such as Ni(OH)(2), Co(OH)(2), MnO2, and Fe2O3. For example, a 3D networked Ni2P nanosheets array via a facile phosphorization reaction of Ni(OH)(2) nanosheets is grown on the surface of a Ni foam. The Ni foam-supported Ni2P nanosheet (Ni2P NS/NF) electrode shows a remarkable specific capacitance of 2141 F g(-1) at a scan rate of 50 mV s(-1) and remains as high as 1109 F g(-1) even at the current density of 83.3 A g(-1). The specific capacitance is much larger than those of Ni(OH)(2) NS/NF (747 F g(-1) at 50 mV s(-1)). Furthermore, the electrode retains a high specific capacitance of 1437 F g(-1) even after 5000 cycles at a current density of 10 A g(-1), in sharp contrast with only 403 F g(-1) of Ni(OH)(2) NS/NF at the same current density. The similar enhanced performance is observed for Ni2P powder, which eliminates the influence of nickel foam. The enhanced supercapacitor performances are attributed to the 3D porous nanosheets network, enhanced conductivity, and two active components of Ni2+ and P- with rich valences of Ni2P.