The system portfolio selection is a fundamental fronti-er issue in the development planning and demonstration of weapon equipment.The scientific and reasonable development of the weapon system portfolio is of great significance for optimi-zing the design of equipment architecture,realizing effective re-source allocation,and increasing the campaign effectiveness of integrated joint operations.From the perspective of system-of-systems,this paper proposes a unified framework called struc-ture-oriented weapon system portfolio selection (SWSPS) to solve the weapon system portfolio selection problem based on structural invulnerability.First,the types of equipment and the relationship between the equipment are sorted out based on the operation loop theory,and a heterogeneous combat network model of the weapon equipment system is established by ab-stracting the equipment and their relationships into different types of nodes and edges respectively.Then,based on the combat network model,the operation loop comprehensive eval-uation index (OLCEI) is introduced to quantitatively describe the structural robustness of the combat network.Next,a weapon system combination selection modelis established with the goal of maximizing the operation loop comprehensive evaluation in-dex within the constraints of capability requirements and budget limitations.Finally,our proposed SWSPS is demonstrated through a case study of an armored infantry battalion.The res-ults show that our proposed SWSPS can achieve excellent per-formance in solving the weapon system portfolio selection prob-lem,which yields many meaningful insights and guidance to the future equipment development planning.