A new style coordinate measuring system based on 3-PSS parallel mechanism was proposed to overcome the drawbacks and weaknesses of traditional Coordinate Measurement Machines(CMMs) and articulated arm CMMs and to realize 3D measurement with only one linear grating and one precision guide. A measurement model,a measuring error model as well as the error averaging effort of the parallel mechanism were investigated. Firstly,a 6-bar measurement model was achieved based on the theory of parallel kinematic mechanism. Then, the influence of bar length error and reading error from the liner grating were analyzed in detail and the hypostasis why parallel structure posses error averaging effort was revealed mathematically. Finally, the prototype CMM was introduced to its design, manufacturing and assemble and the experiment result was provided too.Results indicate that the measuring errors before compensation and instrument calibration in three dimensions are about 0.029 mm in x direction, 0.045 mm in y direction and 0.058 mm in z direction. Obtained results can provide the direction for the design of new CMM protypes.