Abstract: The energy of many modern embedded systems is power-supplied by the batteries. Based on real-time operating system, this paper presents an elastic task model on energy-constrained with universalization, then designs a corresponding real-time scheduling algorithm for guaranteeing the system stabilization and avoiding failtures caused by running out the energy of the non-recharge power-supply according to the rest energy of the battery. The result shows that this model could change the periods of taks according to the rest energy of the battery effectively and timely, so the computation could be completed in their mission times.