Abstract: In order to isolate water layer and leakage layer and reduce pollution at the horizontal section of carbonate reservoir in the Tarim Oilfield,considering the structural characteristics of such reservoir,the completion string for selective completion was designed,and main tool structures and working principle were analyzed.Finally,a technological process that can be operated and controlled easily on site is proposed.The completion string adopts the screen+blind plate+external casing packer+cementing nipple,the tool position is not affected by the well deviation,the cementing nipple can be switched frequently for circulation,and no cement plug left in the casing after operation.The technology has been tested safely and reliably in six wells in the Tarim Oilfield.The field test showed that the technology can be used to oil and gas production at different well sections of horizontal wells in carbonate reservoir,and raise the efficiency of development.