A method for predicting the quantity of pictures that can be taken is applied to a picture-taking function of a digital still camera. Firstly, a lookup table is individually built for different power using operations of a battery according to the operational modes of the picture-taking function. Next, the method looks up the corresponding lookup table according to an obtained battery voltage value of the digital still camera and the operational mode. Finally, a quantity of pictures that can be taken is obtained from the lookup table, and is displayed on a display unit of the digital still camera and is provided to the user. Thereby, the user can change the operational mode to reduce power consumption and take more pictures.