Based on the concept of hybrid mechanism and reciprocal screw theory, a method of structural synthesis of fully-decoupled two-translational and two-rotational (2T2R) parallel mechanisms was proposed and 106 parallel mechanisms were obtained. All mechanisms synthesyzed in this paper consisted of two limbs which were connected with the moving platform and the fixed base. One limb was a single open kinematic chain and another was a hybrid chain. Jacobian matrix of each mechanism was diagonal and there existed a one-to-one mapping relationship between the output velocity of platform and input of actuated joints. Therefore, these parallel mechanisms were fully-decoupled on kinematic solutions, which could avoid some drawbacks of the general paprallel mechanisms in terms of high coupling and complicated control design.