Based on the existing mechanisms, a new kind of two degreeoffreedom planar parallel manipulator with planar translational motion and small inertia was improved and taken as the object of study. Unlike the traditional study method, not only the geometric parameters but also the input of the manipulator are consider as the kinematics parameters, and the design space was obtained by utilizing the theory of geometric model of the solution space. The global velocity indices were calculated in the design space, the velocity atlases of the manipulator were plotted, and the relationship between the velocity and the kinematics parameters of the manipulator was discussed. The results show that: the minimum and maximum velocity indexes ηvmin and ηvmax are inverse to r1, that is r1 is shorter, the velocity performance is better; The ηvmin and ηvmax are proportional to r2, that is r2 is longer, the velocity performance is better; While 0