The dynamic voltage and frequency scaling (DVFS) is one of the most effective mechanism for power management. Firstly, we point out the most shortcomings of the current DVFS mechanisms after detailly analyzing;so we propose a task behavior based DVFS mechanism (TC-DVFS). TC-DVFS has three levels: First, gather the system call information of the task. Second, distinguish the critical system calls and characterize task behavior with them;Third, construct a feature database based on task behavior and guide DVFS according the database. Adding TC-DVFS into linux kernel, experimental results show TC-DVFS reduce 5% miss rate of the correct frequency scaling and 5% power of the system, and also improve 10% performance of the system.