In this study, the virtual network mapping issue in network visualization area and its current research progress are reviewed, and the main issues in admission control and algorithm performance evaluation for existing virtual network mapping algorithm are pointed out. Then the virtual network mapping approximation algorithm with admission control is proposed, and the competitive analysis of this algorithm is provided. Experiment result shows that the proposed algorithm increases the physical network resource load balancing metric and the coefficient of utilization, hence it can improve the virtual network construction request acceptance ratio and the income profit of physical network service provider.