Abstract: With large-scale application of horizontal wells, the stimulation and reform of horizontal wells has been playing a more and more important role in increasing oil/gas production. In order to ensure fully fracturing of multi-stage reservoir in well, make play the capacity of each stage in horizontal section and make the reconstruction more pertinent and more selective, the development of selective acidizing technology for horizontal wells is particularly important. This paper presents a selective acidizing process by dragging coiled tubing in horizontal wells, which conducted experimental analysis and theory study for key operation parameters, and established technical parameters and successfully implemented on DH20-4H Well.