Abstract: Mixed-criticality systems integrate different criticality levels applications and components into a common shared platform. Energy consumption is very important for mixed-criticality systems due to size, weight and volume constraints. Energy-aware scheduling algorithm is the effective method to solve the energy consumption problem of mixed-criticality systems. Existing energy-aware algorithms based on dynamic priority schemes have lower slack time utilization. Fixed priority mixed-criticality scheduling (FPMCS) algorithm is proposed to solve the energy consumption problem of mixed-criticality systems. Firstly, a criticality rate monotonic scheme (CRMS) is proposed to schedule mixed-criticality sporadic tasks. In addition, the scheduling feasibility of CRMS is analyzed and the energy-aware speed is computed. Secondly, the slack time reserved for higher criticality level task is used to re-compute the utilization of higher criticality level task. The dynamically update the utilization of mixed-criticality sporadic tasks method through the method of event triggering is proposed to reclaim slack time generated from the random arrival of sporadic tasks. Thirdly, the speed of tasks is determined by the mixed-criticality sporadic tasks utilization to save energy. Finally, FPMCS algorithm is verified to be feasible by theoretical analysis and experiments. The experimental results show that the proposed FPMCS algorithm can save about 33.21% of energy consumption than existing algorithms.