Abstract: The Shasi 6 sand formation reservoir in Mian 14 area of Bamianhe Oilfield is of high porosity and medium-low permeability, high clay mineral content and strong water sensitivity. In the process of water injection, there are some problems such as high water injection pressure, increasing under-injection wells, low water well utilization rate and poor conventional acidizing effect. In order to improve the qualification rate of water injection in this block,a "clean retarding acid & anti-swelling and increasing injection" system was developed.The comprehensive properties of the system, such as retarding, anti-secondary precipitation and long-term anti-swelling, were evaluated indoors.The experimental results show that the system has the characteristics of long distance and low damage in deep acidification. It has been successfully applied 7 well times in Shasi 6 sand group, and the qualification rate of injection is 100% with remarkable application effect.