A sensor network consists of many low-cost, low-power, and multi-functional sensor nodes. One of the most important issues in sensor networks is to increase network lifetime, and there have been researches on the problem. In this paper, we propose a routing mechanism to prolong network lifetime, in which each node adjusts its transmission power to send data to its neighbors. We model the energy efficient routing with power control and present an algorithm to obtain the optimal flow solution for maximum network lifetime. Then we show that our mechanism can save power consumption and increase network lifetime than the mechanism without power management.