Although the model of DDS (deadline-driven scheduler) is a classical model of real-time system, the space-condition is not included in its original framework. Based on the extension of the original framework of DDS, multi-processes task scheduling with space -constraint is investigated. By studying the parallel model of DDS, the concept of maximal separated task-set, the primary scheduling algorithm and the general scheduling algorithm are presented. In order to formalize the parallel model of DDS, the paper extend duration calculus to DC* with the idea of separation logic, which can express the space-constraint successfully, and give the formalization too.