1. A method for determining frames within multiple frames for use in an electronic device, comprising: obtaining a plurality of frames, wherein the respective frames are captured with a time interval; detecting at least one object within at least two of the frames; calculating an overlapped area corresponding to the object within a first frame and a second frame; and selecting at least one candidate frame according to the overlapped area corresponding to the object, comprising the steps of: determining whether the overlapped area corresponding to the object equals to zero; if the overlapped area corresponding to the object equals to zero, calculating a moving speed of the object according to the positions of the object in the respective frames and the predefined time interval; and selecting candidate frames within the frames according to the moving speed of the object.