A kind of three degree of freedom (3-DOF) parallel machine tool with two redundant actuation is taken as the research object. The inverse displacement equation and velocity Jacobian matrix were first established. After discussing the constraints which influence the size and shape of workspace, the workspace of different locations where redundant actuation located in was obtained by using the method of limit boundary searching, and the workspace boundary of different sections was analyzed. Simulation shows that compared with a redundant drive machine tool, the top and bottom of the workspace of this parallel machine tool is enlarged and filled, which is more regular and can meet the requirements of large workpiece’〖KG-*2〗s process. The research results can be used as reference for the practical application of the machine tool.