Turntable is the main bearing component of truck crane, its structural-load-carrying capacity influences the operational capability directly. This paper adopts the HyperWorks software to make topology optimization for the turntable structure of QY70G truck crane, and carry out the finite element analysis and comparison for the models before and after optimization, which provides an effective method to improve the turntable structure of truck crane. Turntable is one of the important components of truck crane，it bears hoist boom、lifting、luffing mechanism and bob-weight and so on, it is the transfer center of truck crane when it works, the structure will directly affect the lifting performance of the machine. But, the rotary table structure design is affected by the vehicle shape size and installation and space layout. The traditional design method is based the experience of analogy to check by finite element software, it is difficult to get the design scheme which meets the requirements given above and own better strength and stiffness, it also have the disadvantages of long design cycle and large workload. This article is based on the finite element method and structural topology optimal idea, by means of HyperWorks-OptiStruct, makes finite element analysis for the turntable structure of certain QY70G truck crane, and carries on the structural topology in the condition of setted installation location and space, in order to obtain the ideal design plan.