This work focuses on the effectiveness of different metal oxides act as sensing layer in the gas sensor. This is for sensing ethylene (C2H4) gas in fruit ripening detection. The study involved a computational approach, COMSOL Multiphysics whereby the ripeness detector is simulated and characterized. The paper presents a sensitives layer of metal oxides with a thickness of 0.5pm on Lithium Niobate (LiNbO3) piezoelectric substrate for ethylene (C2H4) gas sensing application in order to distinguish maturity level of fruits. The optimum operational frequency is found to be 867MHz by choosing Zinc Oxide (ZnO) as the sensing layer. This paper presents a two-dimensional simulation of Surface Acoustic Wave (SAW) wave propagation, plus this simulation will help in understanding more on the behavior and the most efficient sensing layer material to be used as the gas sensor without having to perform the actual fabrication process.