The paper presents a configurational synthesis method for multi-mode parallel mechanisms based on planar closed-loop chains. Firstly， a planar closed-loop chain with two motion modes is introduced. This chain is incorporated into the realm of parallel mechanisms and serves as the moving platform of the parallel mechanism. By toggling its motion modes， the change in the degrees of freedom of the parallel mechanism can be achieved. Secondly， the definitions of the full configuration and sub-configurations in multi-mode parallel mechanisms are expounded. The screw theory is introduced into the configurational synthesis theory of multi-mode parallel mechanisms. Furthermore， the configurational synthesis principle of multi-mode parallel mechanisms based on the screw theory is put forward. Subsequently， based on the configurational synthesis principle of multi-mode parallel mechanisms and planar closed-loop chains， the configurational synthesis of a class of parallel mechanisms with two motion modes is conducted.Finally， the degrees of freedom of the synthesized multi-mode parallel mechanisms are analyzed by means of the screw theory.