Intelligent negotiation plays an important role in e-commerce. In the research of multi-attribute negotiation, the non-linear relationship between attributes is usually neglected. Multi-attribute multilateral negotiation model with such complex relationship is more practical. In this paper, the building of a multilateral negotiation model of complex contracts with nonlinear dependencies between attributes by applying Multi-Agent System and hybrid intelligent algorithm is studied. And the approximate optimal solution of Nash equilibrium within a certain accuracy range is given. Finally, through simulation examples of multilateral negotiation with two attributes of price and quality, the correctness and validity of the method are verified. The research provides new ideas for intelligent negotiation research.