With the implementation of just one mechanism, variable topology mechanisms can serve the functions of many mechanisms by changing their topology. These types of mechanisms have raised interest and attracted numerous studies in recent years, yet few of these studies have focused discussing of these mechanisms in light of their operation space. As the change of a variable topology mechanism is induced by either intrinsic constraints or constraints due to the change of joint geometry profile, the operation space of kinematic joints and kinematic chains in various working stages is changed in accordance. A theoretic framework based on the concept of the operation space of variable topology mechanisms is presented here. A number of characteristics with regard to the motion compatibility among joints and loops in different working stages are derived, laying a foundation for systematical synthesis of variable topology mechanisms. Design of a novel latch mechanism for the standardized mechanical interface system is given as an illustrative example for the synthesis of a variable topology mechanism.