Power consumption has become a critical issue in designing computer systems. Dynamic power management is an approach that aims to reduce power consumption at system level by selectively placing components into low power states. Time-out and prediction based policies are often adopted in practical systems. However, they have to accurately determine the time in low power state and otherwise the saved power consumption is not worth the loss of performance. In this paper, a power management for multiprocessor systems is proposed to optimally reduce the power consumption of multiple processors.