Abstract: An experimental study with pressure measurement at low speed subcritical and critical Reynolds number range has been carried out for both slender body models with fineness ratios of 6.15 and 11. The results show that if the end of afterbody is far enough from the twin asymmetric vortices region, the muti-vortices system controlled by twin asymmetric vortices at forebody should be not influenced, and the correlations between manual mini-perturbation on the model nose and asymmetric vortex response are also consistent for experimental results of both models. It provides a high Reynolds simulation experimental technique in low speed wind tunnel with increasing the model diameter and decreasing the fineness ratio of test slender model. Based on this simulation technique, the results in critical Reynolds show that the sectional pressure distributions are much different at subcritical and critical Reynolds number ranges. At critical Reynolds number, the side force on the slender body is much lower, and the two-cyclebehavior of the curve C_y vs. γ is no longer existed, therefore the active control technique of asymmetric vortices with a single hole bleed perturbation is useless at critical Reynolds number range.