Facile evaluation of oxygen reduction reaction (ORR) kinetics for massive electrocatalysts is critical for sustainable fuel cells development and industrial H2O2 production. Despite great success in ORR studies by mainstream strategies, such as membrane electrode assembly, rotation electrode technique and advanced surfacesensitive spectroscopy, the time and spatial distribution of reactive oxygen species (ROS) intermediates in the diffusion layer is still unknown. By time-dependent electrochemiluminescence (Td-ECL), here we report an intermediate-oriented methodology for ORR kinetics analysis. Thanks to multiple ultra-sensitive stoichiometric reactions between ROS and the ECL emitter, except for electron transfer numbers and rate constants, the potential-dependent time and spatial distribution of ROS was successfully obtained for the first time. Such uncovered exclusive information would guide electrocatalysts for fuel cells and H2O2 production with maximized activity and durability. This work would pave the exploration of not only the fundamentals of unambiguous ORR mechanism but also the durability of electrocatalysts for practical applications.