Abstract: According to such characteristics of narrow working cabins as small space, long working hours and lack of comfort, a method of upper limb posture assessment based on fatigue characteristics is proposed. First, using the fatigue characteristics of upper limbs from experiments, a 3D kinesiological model of the human body is built up. This establishes an idea for the resolution of this type of question with the finger space coordinate transformation method, then obtains the fatigue characteristic values of different position in the global coordinate system, and finally achieves a physiological parameter definition of human upper limb posture. The human-machine weight of objects is determined by a combination of expert decisions and an analytic hierarchy process. On this basis, in combination with Ant Colony Optimization(ACO) , the layout method for narrow working cabins is created. Finally, a simulation test using Jack software is conducted to verify that the layout method achieves more humanized design requirements.