Abstract: By analyzing the problems of real-time scheduling in mix-criticality systems, a new scheduling algorithm, forward and backward time window partition-criticality factor prior (FBTWP-CFP), is proposed. It can separate the running time windows for the tasks of all criticality levels offline from the forward direction and backward direction and generate the idle windows for the tasks which get the lower priority by the criticality factor for the criticality level changed. The simulation results show that FBTWP-CFP is better than criticality assigned priority algorithm (CAPA) and own criticality based priority (OCBP) in completed tasks number and reduced miss deadline ratio.