This paper is one of the achievements of the researchitem for computer-aided design of tower crane's steel structure.In thepaper,taking the well-base structure as an example,first the method establishing the mechanical model is explained for the base structure ofa movable tower crane.Then the math model of its optimal design andthe N-S figures for the computer program is described and calculatedusing discrete optimal technology.Finally the problems related to thedesign for the base structure of a movable tower crane are briefly illu-strated.