Abstract: We present a low power scheduling algorithm for mix tasks which is based on constant bandwidth server and orients to the mix tasks set in hard real-time systems, named CBSMTLPSA (constant bandwidth server mix task low power scheduling algorithm). The mix task set consists of the periodic tasks with the limit of deadlines and the aperiodic tasks with the requirement of the response time. The CBSMTLPSA algorithm, which combines the DVS (dynamic voltage scaling) technology with the DPM (dynamic power management) technology, is two phases algorithm. To take advantage of the processors resources, it should determine the offline speed of the task in the offline phase. It reclaims the slack time from already completed periodic tasks as well as from the server, and uses the DVS technology to adjust the speed of the processor to reduce the energy consumption in the online phase. In addition, in order to further reduce the energy consumption, it should determine whether the DPM technology is used to save energy, when the processor is in idle status. Simulation results show that the CBSMTLPSA algorithm consumes 6.02%-34.14% less energy than that of the CBS/DRA-W (constant bandwidth server for dynamic reclaim algorithm base workload) algorithm. The product of energy consumption and response time of aperiodic tasks of CBSMTLPSA algorithm is about 5.86%-34.06% lower than the CBS/DRA-W algorithm.