The method of dynamic voltage scaling(DVS) is an efficient technology for saving energy.This paper put forwards a near optimal strategy on multi core processor using DVS.It changes the problem of voltage scaling to the problem of slack time allocation.It detects the slack time based on task structure firstly.Aiming at different kinds of slack times

it then uses relevant allocating method such as parallel compensate algorithm.Result of the experiment indicates that the strategy of this paper can decrease the energy consumption efficiently and has low complexity.