A thermoacoustic prime mover, due to its simple structure, would serve as very desirable systems because it can be driven with the waste heat such as an exhaust gas from engines, and with heat from the nature such as sunlight and a geothermal heat. The advantages of this prime mover are the flexibility for various heat sources as an external engine and a possibility as the cost effective system due to simple structure. On the other hand, the energy conversion from waste heats to more effective energy such as motion energy or electric energy is desired in the automotive area because of demands of improvement of fuel efficiency. In this research, our interests focused on the performance improvement of looped-type thermoacoustic prime mover by varying stack configuration, inserting membrane to cut off the DC flow and adopting equipment of phase adjustment between pressure and velocity of gas oscillation. The experimental setup we use here is operated under the condition of a 4.2m loop length, the working fluid is argon, the 75Hz operating frequency and stacked screen mesh as a stack configuration. To improve the total thermal efficiency, various efforts have been made experimentally to grasp the optimization of stack structure which plays an important role to energy conversion. Finally, discussions on the future application of prime mover aiming to utilize the waste energy of exhaust gas are made and, by installing a membrane of natural rubber inside the tube, the acoustic intensity has increased by 20%.