Abstract: In this paper,we propose a new approach to some two machine shop problems,which gives so called bi directional scheduling algorithms for these problems in terms of open shop,job shop,mixed shop and open shop with 3 stage jobs.The main idea of the new approach is that all operations of jobs are either scheduled forward successively from time zero,or scheduled backward successively from the time which is a lower bound of makespan.As the advantages fo our approach,constructions of the optimal schedules for these problems are greatly simplified,and the optimality proofs are simplified as well.\;