Abstract: Due to the problems in the operation of the Stirling engine caused by a high fluctuation of the low density gas in China, a set of a thermal accumulated ty pe low density gas power generation system was designed and an experiment study on the thermal accumulation performances was conducted.The study showed that t he thermal accumulator would have excellent thermal accumulated performances in the heating, operation and stop stages.The thermal accumulator could store the the rmal when the low density gas generated too much thermal in the porous medium and could release the thermal when the low density gas generated less thermal in the porous medium.Thus the thermal accumulator could effectively reduce the impacts to the Stirling engine caused by the fluctuations of the gas density.Under the perform ances of the thermal accumulated ball with particle size of 10 mm, the thermal accumulated effect would be the best.Meanwhile, the fluctuation of the output power from the Stirling engine would be also reduced remarkably.