Abstract: Construction without middle drift is a novel method for the double-arch tunnel, and the blasting excava? tion of the subsequent tunnel will have a vibration impact on the lining structure of the antecedent tunnel. Taking the Chenjiachong tunnel of Chuxiong-Dayao expressway in Yunnan province as an example, it studies the blasting vibration control technology of double-arch tunnel without middle drift in red-bed soft rock. Firstly, the three main influence factors of the double-arch tunnel blasting are analysed: the distance between blasting sources, the explosive charge and stress release. Then automatic vibration monitoring is carried out in the corresponding area of the antecedent tunnel aiming at the three-bench、excavation and two-bench excavation of the subsequent tunnel, and the blasting vibration law of the V-level surrounding rock of the red-bed soft rock is obtained by regression analysis of the monitoring data, the explosive dosage of cutting hole, the numbers of nonel detonator segment and economic energy unloading holes as well as the hole spacing are obtained by back analysis,a layout of the blast holes and blasting scheme are established to meet the needs of the site. The field monitoring data show that the revised critical value of vibration velocity and the optimized blasting scheme meet the safety requirements and guarantee the smooth excavation of the subsequent tunnel and no vibration induced cracking in the concrete secondary lining.