The present invention provides a potential energy regenerating system and method and an electricity regenerating system and method. The potential energy regenerating system comprises: a liquid storage bag module, having a compressible liquid storage bag; a pipe line module, including a liquid access opening switch control device and a pipe line connected to the liquid access opening control device; a liquid storage tank module, including a liquid storage tank with a bottom higher than the highest position where the liquid storage bag module can reach; and a squeezing weight module, including a squeezing weight mass and a control device, wherein the squeezing weight mass is placed on a top of the compressible liquid storage bag, and the control device controls to lift and release the squeezing weight mass. The electricity regenerating system uses the foregoing potential energy regenerating system to generate electricity.