Aiming at the problem for task-processor assignment in distributed computing,two improved algorithms based on A* algorithm are proposed.By analyzing the principle of A* algorithm,the search tree model of applying A* algorithm to task assignment problem is obtained,and by dividing the search tree as evenly as possible among the processing units and by avoiding unnecessary nodes extension,the optimal solution is obtained. The experimental results show that, compared with the traditional A* algorithm, the proposed two improved algorithms can not only save memory and task execution time by reducing search space,but also improve the speedup performance of algorithm execution by parallel assignment.