Abstract: In order to ensure the water, power matching relations between upstream and downstream of cascade hydropower stations, under power market conditions, it is necessary to carry out researches on short-term optimization operation mode of cascade power stations facing the spot market and exploit the matching method of water quantity and electricity quantity under the unified bidding mode of cascade power stations. This paper focuses on electricity spot market oriented joint optimization scheduling problem. Based on an analysis of the correlation between the power demand and the clearing price in the power market, the paper proposes using the power demand process to drive the optimal operation of cascade hydropower stations. By taking the cascade hydropower stations from Pubugou reservoir to Tongjiezi reservoir on Dadu River as an example, this paper constructs an expected power maximization model considering price-fluctuation within a day. A newly proposed dragonfly algorithm（DA） is applied to model calculation. A typical day data is selected as case study. The simulation results show that（1） the operation modes such as water level process and output process of the cascade power station obtained by DA conform to the general dispatching laws, the calculation time and efficiency meet the practical requirements（about 120 s）, these indicate that DA can be used to solve the short-term optimization scheduling problem of cascade hydropower station with high dimension; and（2） there is a strong correlation between power demand and clearing price, especially the occurrence time of peak and trough of the two is highly consistent. It indicates that the optimal operation of cascade hydropower station driven by power demand can guide the cascade hydropower station to generate more power during the period of large demand. Therefore, the expected power generation maximization model established in this paper is feasible, which can achieve the pursuit of greater economic benefits while ensuring the water, power matching relations between upstream and downstream of cascade hydropower stations. It can be used as a reference for the electric quantity declaration scheme of the hydropower system participating in the spot market bidding.