Knowledge-sharing is beneficial to improve group performance. However, to the individuals possessing different knowledge potential, their own performance relies on the knowledge-sharing mechanism. Firstly the related factors which have influence on the knowledge-sharing are analyzed. Then a model is built to simulate the impact of knowledge-sharing mechanism against the group performance and individual’s joining the organization in dynamic scene. The result implies that behavior of knowledge sharing is mainly under the influence of the balance between anticipated benefit and cost of individuals, and so on. The construction of more scientific and proper knowledge-sharing mechanism can decrease the cost of knowledge sharing, keep up the balance between the interests of individuals, and improve the group performance.