The invention discloses a method and a device for measuring and calculating the checking power and stored power of a power station. The method comprises the following steps that: 1, remote sensing equipment measures the water level data of a reservoir, an ultrasonic flow meter measures a day-by-day power generation flow Qday, and output acquisition equipment acquires day-by-day average output Nday; 2, a calculation server processes the data to obtain a ten-day average power generation flow Qten-day, a ten-day average power generation head Hhead and ten-day average output Nten-day; 3, the calculation server obtains Kten-day by utilizing a hydraulic power formula; and 4, the calculation server measures and calculates the checking power and stored power of the reservoir in a corresponding time bucket. The water level data, the day-by-day power generation flow Qday and the day-by-day average output Nday of the reservoir are measured in real time, and the Kten-day is calculated by combining the real-time data and the hydraulic power formula, and is close to an actual value; and compared with a fixed K value, the Kten-day has the advantage that the accuracy of the measured and calculated checking power and stored power of the power station is greatly improved.