The atmospheric cutterhead is a new type of cutterhead with high technical difficulty. Compared with the conventional cutterhead, the spatial structure of the atmospheric cutterhead is more complicated, and a mature design theory has not yet been formed. This paper presents an atmospheric cutterhead design method for slurry shield machines. The method was divided into three steps: (i) design load analysis; (ii) multiobjective topology optimization; and (iii) evaluation and selection of cutterhead structures. Based on topology optimization theory, four types of cutterhead structures with different numbers of radial arms are obtained. The performance of the cutterhead was evaluated by stress, deformation, vibration mode, opening situation and space complexity, and the five-radial arm cutterhead was determined to be the best solution. Analysing the actual tunnelling parameter data shows good engineering adaptability. This paper provides a reference for the optimal design of the atmospheric cutterhead of slurry shield machine.