On the basis of working characters, an integrated and refined 3-D finite element analysis for working mechanism was presented. Take excavator as an example, the 3-D model of working mechanism was established. Based on assessment of preliminary finite element, the way of establishing finite element model has been determined. Selected five typical working statuses, the stiffness, strength and modal analysis was made for assembled working mechanism, and test for actual product has been done. The results showed that stress distribution of work mechanism could clearly explain failure cause and the result could be applied as the references for the working mechanism design. The excavator design method has been improved and a new approach was provided for similar product design and analysis.