【正】 The accelerator beam transport operator presents the evolution of beam phasespace point with given transport elements and given initial point,while the inverse beamtransport operator presents the evolution of beam phase space configuration with giveninitial phase space geometry.Therefore,it is necessary to develop a general theory be-tween these two operators.Several concrete examples are worked out in detail to showthe practical applications of such a theory.This paper deals with the linear acceleratorbeam transport operator,and a theorem of finding the inverse linear beam transportoperator for both autonomous and nonautonomous accelerator dynamics is developed.