Abstract: In view of the threat of the space-based high-energy laser to the geosynchronous orbit satellites and the demand for the protective design of high-value GEO satellites, the theoretical analysis and the numerical calculation are conducted to evaluate the damage effect of the space-based laser (SBL) on the GEO satellites according to the development of the tactical laser weapons. It is shown that the SBL with an output-power of 10 kW can damage the satellites 50 km away on the following vulnerable parts in a descending order, the thermal control materials on the satellite surfaces, the solar arrays, the carbon fiber enhanced composite, and the optical sensors. Enlightenments can be drawn from the analysis results: the threat of the SBL to the GEO satellites is realistic; the most effective protective design should focus on the weak links; protective measures should be taken on the equipment level, the sub-system level and the system levels, respectively, to improve the robustness of the satellites; active and passive methods should be adopted comprehensively to enhance the protection against the SBL.