The thermoacoustic engine is a green technology that can harness solar and waste energy to produce electricity in combination with a linear alternator and can be used as a heat pump. This type of engine is particularly appealing because it has a simple structure and contains no mechanical moving parts, consisting only of a stack sandwiched between heat exchangers within a resonator. When the temperature gradient on both sides of the stack reaches the critical temperature (onset temperature), the working gas oscillates spontaneously. Due to viscous loss in the system, a high onset temperature is typically required to induce gas oscillation in a thermoacoustic engine. To address this challenge, a method has been developed to reduce the onset temperature by increasing the number of unit stages comprised of stack and heat exchangers, which has enabled the engine to utilize low-grade thermal sources. However, this method has only been applied to traveling wave thermoacoustic engines, and the standing wave one which provided a more compact and straightforward structure has not yet been explored. This study aims to know the influence of the number of unit stages in a standing wave thermoacoustic engine that can impact both the onset temperature and its acoustic field. The onset temperature is predicted by utilizing a fundamental equation of hydrodynamics and then using DeltaEC software to investigate the acoustic field throughout the engine. The result showed that an appropriate number of unit stages in the standing wave thermoacoustic engine need to be considered in order to get the optimum engine.