Abstract: Based on drill string dynamics theory and system simulation software, the horizontal well's dynamic drag and torque were studied. According to the calculation result, the paper designed three optional design cases and finished its calculation and analysis. Some valuable reorganizations was gained such as this dynamics method can reflect the fluctuation of drag and torque, the tool number has a marginal value and is not the more the better, and proper location must be obtained through the scientific computation. The drill string dynamics software can provide support for choosing the location of friction reducer.