In order to improve the accuracy and efficiency of 3D printing, a slicing direction and thickness optimization method based on group search optimization (GSO) algorithm is proposed. Firstly, according to the geometric characteristics of STL data model, the relationship between volume error, production time and layered direction and thickness in 3D printing is analyzed, and a weighted objective function is constructed. Then, the GSO algorithm is used to optimize the solution space to obtain the optimal slicing parameters. The experimental results show that this method can effectively reduce the volume error and improve the printing efficiency.