In this work, a binder-free electrode Mg-doped NiCoP/Ni foam (MNCP-x/NF) was prepared via hydrothermal and phosphorization process, in which echinoid microflower-like MNCP-x was densely loaded on the NF skeleton. By regulating the Mg2+ doping amount, remarkable enhancements in the morphology, mass-loading of MNCP, electrode conductivity and overall electrochemical capacitive properties of MNCP-x/NF have been achieved. Particularly, moderate doped MNCP-0.5/NF exhibits the best energy storage performances with a superior specific capacity (4461 mC cm-2 @ 2 mA cm-2), acceptable rate capability (retaining 50.1% @ 50 mA cm-2), and striking cyclability (retaining 83% over 5000 cycles). Moreover, a solid-state asymmetric supercapacitor constructed with MNCP-0.5/NF as cathode, graphene hydrogel/NF (GH/NF) as anode, PVA/KOH gel as electrolyte, outputs the notable energy density of 39.8 Wh Kg-1 (1.8 mWh cm-3) and power density of 16674 W Kg-1 (750 mW cm-3), companied by a superior cyclability (retaining 87% over 5000 cycles).