Owing to their high theoretical specific energy density offered by the metal-oxygen chemistry, rechargeable metal-air batteries have garnered much attention in recent years. The major technical challenge of the batteries lies in developing novel low-cost and durable bifunctional oxygen electrocatalysts. In search of such materials, Linear sweep voltammetry (LSV) and Electrochemical Impedance Spectroscopy (EIS) are conventional techniques used to characterize their catalytic activity. However, due to the complicated multi-step and parallel reactions occurring simultaneously at the oxygen electrode, the classical methods of data analysis are not applicable, such as Levich Equation, Equivalent Circuit method. In this paper, we proposed a physics-based model to include multiple oxygen transfer pathways and further estimate parameters from experimental data of Lanthanum Cobalt Oxide (LCO) catalyst at a rotating disk electrode (RDE). The model is capable to predict reaction kinetics of both sequential two-step oxygen reduction mechanism and direct one-step four-electron transfer mechanism, as well as peroxide disproportion reaction. Nonlinear parameter estimation technique is applied to obtain the relevant kinetic and transport parameters. The modeling results will give experimentalists a guideline in understanding the ORR mechanism for LCO catalyst.