Abstract: The present invention discloses a power system reliability assessment method considering optimized scheduling of cascade hydropower stations, by which the reliability of the power system is improved, comprising following steps: establishing power system optimization models; inputting the sequential wind speed, runoff and load data within 24h; in accordance with reliability parameters of units and by the sequential Monte Carlo method, sampling the state durations of three kinds of units and segmenting the state durations on a 24-hour cycle; calculating the sequential output of wind farms within 24h according to wind speed data and the state of wind power units; calculating the hourly loss-of-load, according to the state of wind power units and thermal power units as well as the optimization models; optimizing for 365 days according to the method described in the step 4, and calculating reliability indices; and determining convergence or not, and if not, continuously repeating the steps S3 to S7 until convergen