Thermoacoustics is concerned with the interaction of thermodynamics and acoustics. This interaction can bring numerous innovative applications in power generation and refrigeration. Thermoacoustic phenomenon can be classified into two main categories: the first one where the thermal energy (heat) is transformed into acoustic energy (sound) is called thermoacoustic engine; the second type, where the acoustic energy is transformed into thermal energy, is called thermoacoustic refrigerator or heat pump (1). The main objective of this work is to inspect the effect of the main geometrical parameters of the thermoacoustic heat engine on the performance, in order to increase the thermal efficiency. In this work, the thermoacoustic heat engine is modeled using the DeltaEC software (2). The results show that the efficiency of the thermoacoustic engine can be increased from 9.6 % to 16 % by changing the mean pressure, stack spacing, stack mid-position and stack length. The physics behind these changes and the suggested design guidelines are presented.