Abstract: Definitions of the functions of management differ from the classical Fayol theory to the modern management theory. Among them，the function orientations of planning and decisionmaking attract widespread concern. To clarify the relationship between them，it is necessary to explore their different practical backgrounds，analyze the deep motivation of their evolvement. And on the principles of unifying history and logic，we redefine their functions and the relationship and hold that decisionmaking is the premises of planning，and planning is the continuing of decisionmaking process. Besides，decisionmaking can be further divided into preplanning decisionmaking process，which gives planning a clear direction and whileplanning decisionmaking process，which makes up for any possible failure in planning.

Key words: management theory, management functions, planning, decisionmaking, enterprises