To solve the problems of low accuracy and folding rate of the main reflective surface of a traditional solid reflector mechanism, a deployable solid reflector mechanism was designed in this paper. First, the configurations of four types of deployable units were proposed, and their degrees of freedom were analyzed. After comparing and analyzing the advantages and disadvantages of the configuration schemes, configuration scheme 4 was defined as the basic configuration of the deployable unit, and its structure and deployment principle were designed. Then, based on the D-H coordinate transformation, a basic deployable unit kinematic model was established. According to the geometric constraints, the position vector equation was established; the relationship between rotation angles was established by the vector closed-form projection method; and the position, velocity, and acceleration were analyzed. Simultaneously, ADAMS software was used to establish the mechanism simulation model and verify the correctness of the kinematics analysis. Finally, based on the relationship between the rotation angle and the structure size of the mechanism, the effects of rotation angle and structure size on the folding rate were analyzed, and the rotation angles and of a 2.2 m deployable solid reflector mechanism are determined to be 78° and 30°, respectively. The center disk radius, the longitudinal dimension of hinge support hole, the transverse dimension, the longitudinal dimension of the switching link, and the folding rate are 245 mm, 8 mm, 40 mm, 18 mm, and 0.326 respectively, which provide a reference for the design of the deployable solid reflector mechanism.