Four similar hole models with the aperture of 3,1,0.5 and 0.3mm were selected,with the fluid regarded as continuous medium to investigate the effect of Knudsen number on the characteristics of microscale similar flow.The mass flow rate coefficient was calculated by numerical simulation when the Knudsen number of fluid with each scale pore was variable and constant at the same Reynolds number,and then the internal flow field was analyzed.The results show that when the Knudsen numbers of the four hole models are equal,the internal flow fields and the mass flow rate coefficients of different scale pores show a better similarity at the same Reynolds number,so it is required to ensure the same Knudsen number to get more accurate results in investigating the flow characteristics of microscale structure by amplificatory models.