The definition and creation of assembly cells is one of the most important fundamentals of production general process planning. Currently, only a few researches made on this issue are still based on 2D engineering drawings at home and abroad. Moreover, during practical production general process planning, process designers partition assembly cells especially for complex structure on 2D engineering drawings by manual way. These methods cannot evidently meet the demands of 3D digital technology development and applications for modern products. In this paper, the techniques of assembly cell partition for complex structure are investigated based on its 3D modeling. The 3D Process Split Space is defined and constructed respectively, and the methods of the component recognition and assembly cell modeling are established. The proposed techniques are initially developed and verified on the CATIA V5 system.