Abstract: In the process of well drilling, there is a certain deviation between the actual hole trajectory and the design value. When the deviation is larger, modifying design shall be carried out on the hole trajectory to be drilled in time in order to reach the target. No matter whether the original design is two dimensional or three dimensional, the trajectory modifying design in the process of construction shall be three dimensional. The physical model of inclined plane arc-straight line-inclined plane arc method for the three-dimensional trajectory modifying design of horizontal well which is put forward for the slide bit feeding and steering drilling system was established. Then, physical model and mathematical model of two three-dimensional horizontal well trajectory modifying design methods which are more suitable for rotary steering drilling system (namely quadratic function method and elastic string connection method) were put forward. Finally, the potential value and the problems to be solved were analyzed.