Abstract: The method to optimize the parameters of length and temperature difference of thermoacoustic regenerator is studied. Based on the linear thermoacoustic theory, a normalized parameter named as the regenerator operating factor is extracted. The regenerator operating factor and relative hydraulic radius set up the quantitative relationship among the working frequency, length and hydraulic radius. The thermoacoustic device under difference frequency could work with same efficiency of thermoacoustic transfer by adjusting the ratio of radius dimension to the axis dimension. Above result is of significance to guide the miniaturization design of the thermoacoustic device. Finally, the regenerator operating factors for two types of typical thermoacoustic devices are optimized and their optimal regenerator parameters of length and temperature difference can be obtained.