To construct the disaster resistance of a power system， firstly， power grid design criterion should be improved to strengthen the key transmission corridors; secondly， generation planning of power supply should be properly located. The impact of adverse weather on a power grid is discussed. Brostr⒐m model and the improved model are proposed and used to study the transmission line ice load. The accuracy of ice load calculation is the key point because it affects the line outage rate much more than other factors. A fuzzy inference system is built to model the relationship between line outage rate and the three logic variables（wind load， ice load， and line flow level）. Power system reliability is assessed under the conditions of adverse weather and extreme adverse weather conditions. Two design strategies on disaster resistance power system are tested in a five-bus two-area system， one is for improvement of power grid design criterion， and the other is for proper placement of planed generations. These two strategies have different impacts on system planning results.