Dynamic behavior of a variable stroke swash plate mechanism is analytically and numerically investigated. Deriving a simple degree of freedom model, we propose a dimensionless arm length to characterize dynamic stabilities of the swash plate angle. We then make a comparison between two types of constraints of the swash plate: one fixating the plate with the swing component and the other linking it with the followers in a frictionless manner. It is numerically shown that the fixed-type constraint improves the stabilities of the mechanism while the frictionless-type constraint makes the mechanism destabilized. An equivalent design technique is also proposed to convert optimal specifications between the different types of the constraints.