A method of design for the baffle of the Ritchey-Chretien (R-C) system used in space remote sensor is presented. A numerical method is provided to determine the lengths and diameters of the baffles. A stray radiation calculation method based on the feature of the R-C system is given for estimating stray light performance in the well-baffled R-C system. The calculation result of the point source transmittance (PST) is used to evaluate how the stray radiation is suppressed in this system.