Aiming at the problems of high injection pressure of water injection wells and under-injection of reservoir in an oil field, a long-lasting acid system was developed by compounding three main agents and related additives on the basis of analyzing the mechanism of reservoir contamination. A series of evaluation experiments of this long-lasting acid were carried out at the formation temperature. The results show that the dissolution rate of the long-lasting acid to the field rock chips for 2 h is 24.4%, and the dissolution rate to the quartz for 2 h is only 0.75%; the dissolution rate of the long-lasting acid system and the rock chips reacted for 1–3 h, and the dissolution rate increased from 14.63% to 31.56%; the inhibition rate of the long-lasting acid to the calcium fluoride, fluorosilicates, and hydroxides is 50.26%, 74.21%, and 78.63%, respectively; respectively, the addition of long-lasting acid accounted for 1 and 2% of the surface fraction. After adding 1% and 2% of surfactant respectively, the surface tension of LCA is 21.86 mN/m and 21.03 mN/m; the corrosion rate of LCA on N80 steel sheet is 4.10 g/(m2·h); the anti-expansion rate of antiexpansion agent used in LCA is 91%; the LCA is applied to 6 wells on site and the effect of injection increase is remarkable.