To give out the stability requirements of every components in the multi-pass amplification system of a large laser facility, a ray- tracing software was developed by using the method of 3×3 matrix and algebra. Using the developed software and by establishing a mathematical model of the layout of TIL, which is a multi-pass high power laser facility, the task of analyzing the relations between the stability of any individual optical component and the position of the beam focus on the target has been fulfilled.