The motion accuracy of a platform based on two compensated flexible four-bar linkages was researched and three error sources,namely, batten size error, the sphere center distance error of ratio lever and the assembling angle between the inner and external battens were analyzed. A semi-beam model was established to analyze the deformation of the batten and the relationship between working displacement and coupled displacement. The expressions of the platform straightness error and the limiting coupled displacement error which was concerned with the platform displacement and the batten sizes were derived. Finally,an autocollimator and a high precise measuring head were used in the measurements of the platform straightness and the coupled displacement. The experimental results show that the straightness error is smaller than 1.5″ and the coupled displacement error is less than 13.7 μm when the stroke of the displacement platform is no longer than 5 mm. It is proved that the platform works with high motion accuracy and the experimental result is consistent with the analysis results.