Multi-MA (Mobile Agents) cooperative system leads to flexible and efficient solutions to distributed system. However, many research works today are not suitable to dynamic network environment. Based on the modeling of Multi-MA cooperative system and analyzing of MA's behaviors, we give some new ideas and a theoretic model on fuzzy knowledge representation and exchange, in which some key problems such as fuzzy belief composing and contradiction coordinating are solved. With the help of some detail simulation experiments on dynamic network topology discovery, we prove the model's availability and efficiency.