In this work, the principle of metamorphic mechanism is optimized for product design based on the variable topological structures. A metamorphic element consisting of kinematic pair and kinematic size is proposed firstly. A new configuration synthesis strategy for feed mechanism is performed in view of the translocation, inversion and duplication variation methods. The metamorphic elements are obtained by means of the decomposing the source metamorphic mechanism. A novelty configuration scheme based on constraint variation features is established by the solution of constraint relationship of metamorphic elements, and three kinds of configurations are synthesized. The comparisons of kinematic performances between source mechanism and new mechanism configurations are carried out using kinematic simulation. Results demonstrate that proposed strategy can synthesize successfully multiple types of the metamorphic mechanisms to meet the demands of functional targets.