Based on the characteristics of launch window, an algorithm to calculate the launch window for space rescue mission was deduced. The problem of the launch window was divided into the plane window problem and the phase window problem. Analytical models of the two problems were established, and the analytical result of launch window was obtained. The launch windows of launch points with different latitudes in the same longitude were described with visualization curves, which served as the basis to calculate and analyze the launch window for space rescue mission.