Abstract: Regenerator is a key part of regenerative cryocoolers,and it gives predominant contribution to the performance of cryocoolers. As a result,it is very important to pay more attention to researching influencing factors of the performance and optimizingstructural parameters in the regenerator. According to the classic thermodynamics and fluid mechanics,two similarity norms—Valensinumber(Va) and Oscillating Peclet number(Pe_ω) —are deduced to study the flow and heat transfer characteristics in regenerators,based on which a multi-layer mesh regenerator is proposed. A simulation by Regen3.3 is conducted to testify the analysis of the regenerator. The results show that the packed pattern of multi-layer plays a significant role on the performance of the regenerator,an appropriate packed pattern can improve the COP. Finally,the packed pattern of Case. 5 multi-layer regenerator is the best and it can provide 2.8W cooling power at 45K while the input PV work is 61.6W.