In current data center, virtual machines may experience severely degraded performance due to the competing of network traffic on shared physical links. This situation is mainly caused by unreasonable and unfair allocation of the bandwidth resource. This paper presents a schema based on the idea of non-cooperative game theory in the field of microeconomics for dynamic bandwidth resource allocation between virtual networks. By modeling virtual networks as competing players and giving the pricing mechanism which decided by the physical substrate network and to guarantee efficiency, the schema can achieve optimal bandwidth allocation at the Nash equilibrium point of the game. We prove that the scheme admits a unique equilibrium point. Experimental results show that the bandwidth allocation between virtual networks is efficient and fair.