The basic ant colony optimization algorithm was improved by introducing the Logisti-chaos model and a strategy of protecting optimal ant.The factors influencing movement precision were discussed in the design of plane mechanism generating angle-displacement of connecting-bar.The fuzzy robust design model was established

and a fuzzy robust design example of plane mechanism generating angle-displacement was given based on ant colony algorithm.When the design parameters including the rod-lengths of plane mechanism were solved

the manufacture tolerances of each rod of mechanism were determined.The robustness of motion precision can be insured by the new fuzzy robustness method put forward.