Many heuristic-based approaches have been applied to finding schedules that minimize the execution time of computing tasks on parallel processors. Particle Swarm Optimization is currently employed in several optimization and search problems due its ease and ability to find solutions successfully. A variant of PSO, called as Improved PSO has been developed in this paper and is hybridized with the AIS to achieve better solutions. This approach distinguishes itself from many existing approaches in two aspects In the Particle Swarm system, a novel concept for the distance and velocity of a particle is presented to pave the way for the job-scheduling problem. In the Artificial Immune System (AIS), the models of vaccination and receptor editing are designed to improve the immune performance.