The undesired shifting phenomenon(USP) occurs easily under the braking or climbing conditions etc., and its impact is the discomfort to the passengers or cause of vehicle's state contrary to the driver's intention, meanwhile, the wear of the clutch and synchronizer is increased, so their lifetime are greatly shortened. To the vehicle with dual clutch transmission (DCT), undesired shifting phenomenon will lead to frequent and unnecessary actuation of synchronizer for the use of pre-engagement synchronizer in the shifting control; therefore, its occurrence should be eliminated as far as possible. In this paper, the process of the undesired shifting of the vehicle with DCT is elaborated, then the generating cause of USP is described based on directed graph. The eliminating method through judging the changing track of coordinate point composed of the throttle opening and velocity is presented, in which the driver's intention, vehicle's running state and their internal relationship are considered comprehensively. In addition, on the basis of undesired shifting control method, the normal downshifting control method in emergent accelerating condition is formulated by fuzzy logic control. The validated results of the eliminating method under the accelerating, braking and urban cycle conditions prove that the undesired shifting can be avoided. Furthermore, the control method can be conveniently implemented on software and hardware and applied in real vehicle. Simultaneously, the relevant results of the emergent accelerating condition show that the normal control of downshifting process can be implemented based on accurate identification of driving intention.