System-of-systems contribution evaluation is an important part of the development of weapon system construction. The system-of-systems contribution’s connotation and characteristics are analyzed, such as the complex structure of the system and uncertainty information. A contribution evaluation approach for weapon system-of-systems based on evidential network is proposed to address these challenges. The network structure model and belief rule base according to the experience of specialists are built. On this basis, the rule based inference methodology is used to infer the operational efficiency for different weapon systemofsystems. Finally, a case study of joint landing campaign weapon system-of-systems is conducted based on the typical foreign weapon to verify the feasibility of the proposed approach. This approach can support decision-making in the fields of national defense, such as the argumentation of weapon demanding and the programming of system development.