Co, Fe, Ni-based (oxy)hydrooxysides have emerged as oxygen evolution reaction (OER) catalysts in alkaline media. Coupling conducting metals or alloys with Co,Ni,Fe-based (oxy) hydroxides can promote the OER activity. CoCrFeNiAl high-entropy alloy (HEA) solid solution fabricated by high-energy ball milling is a potential support for Co,Fe,Ni-OOH OER catalyst. The surface –engineered CoCrFeNiAl HEA via one-step HF treatment can achieve an OER current density of 10 mA cm−2 with overpotential (η) of 243 mV and a Tafel slope of 56.8 mV dec−1 in 1M KOH solution. After further surface self-reconstruction of active sites induced by in-situ electrochemical activation, the as-obtained HEA supported Co,Fe,Ni-OOH delivers a current intensity of 10 mA cm−2 at η of 176 mV and a Tafel slope of 52.7 mV dec−1 and retains its electrocatalytic activity at a current density of 10 mA cm–2 for 11 h.