Abstract: In horizontal well design, there are certain errors on such aspects as reservoir depth, location and distribution between the designing goals and the real conditions, and this affects the application results of the horizontal well. However, such errors can be minimized and even eliminated by using geo-steering technology. This paper describes the concept, composition and characteristics of the geo-steering drilling technology. In Gao7 block, as the pay zone thickness is thin and the fault location is not clear, geo-steering drilling technology was adopted to monitor the formation resistance and determine the well trajectory error during drilling. Unfortunately, well trajectory was not adjusted timely according to the log data during drilling, and this led to the hole being drilled away from the pay zone. It is recommended that when the geo-steering tool is used, the well trajectory should be adjusted timely according to the log data so as to keep the trajectory in an ideal position in the pay zone.