Abstract: Horizontal well technology was applied to tap remaining oil in later high water-cut stage in the south zone of Liangjialou Oilfield, and remarkable result has been obtained.High level has also been reached in many aspects including geological design of horizontal well, reservoir engineering study and management. 6 horizontal wells were successively put into production whose initial oil rate was 12 times as much as adjacent old wells’. Average raised oil of single well reached 1.5×104t, and oil recovery coefficient raised by 5. 0%. In one word, horizontal well technology is a kind of major measure to tap remaining oil in later high water-cut stage, and should be extensively popularized.