Unraveling a descriptor of catalytic reactivity is essential for fast screening catalysts for a given reaction. Transition metal (TM) compounds have been widely used for oxygen electrocatalysis. Nevertheless, there is a lack of an exact descriptor to predict their catalytic behavior so far. Herein, we propose that the bond-energy-integrated orbitalwise coordination number ([Formula: see text]), which takes into account both geometrical and electronic structures around the active site, can serve as a simple and accurate descriptor for catalysts consisting of TM oxides (TMOs) as well as avoid excessive computation burden. This descriptor exhibits a strong scaling relation with the activity in oxygen electrocatalysis, with a goodness of fit higher than those of the usual coordination number (cn), the generalized coordination number ([Formula: see text]), and the orbitalwise coordination number (CN). Especially, the theoretical prediction made by the [Formula: see text] descriptor is very consistent with experimental results and universal for various TMOs (e.g., MnO and RuO), enabling the rational design of novel catalysts.