We present the new dispatching rules of job shop scheduling with alternative machines in order to improve the schedule performance measures, which are mean completion time, mean tardiness, mean work in process and mean shop utilization. Four new dispatching rules and eighteen existing dispatching rules are examined in those performance measures of job shop scheduling at the three levels of the probability that operations can have alternative machines. Through computer experiments, we explore the best dispatching rules and the improvement of solution under those levels. These results provide guidance for the practitioners to choose dispatching rules and for the researchers to develop new rules for job shop scheduling with alternative