The static stiffness characteristic of parallel machine tool is an important factor and reference for machine design and optimization. The static stiffness characteristic of 3-TPT parallel machine tool is researched in this paper. The structural analytical model of machine tool is built by ANSYS software, which has two different work positions and three kinds of different workloads. The details of analytical process and method are provided, and the deformation conditions and the laws of stiffness variation are got. The main factors of static stiffness are obtained, so it provides an important reference for modifying structure of machine tool and relative research.