The key links of power optical networks play an important role in the security and reliable protection of quality of service. Research on the key link identification method helps to improve the efficiency and accuracy of the identification process. In this paper, we first measure the shortest path sensitivity in the network. Then the shortest path length between network nodes is calculated to study the effect of link state deterioration on network performance. Next, based on three different targets, such as minimum hop count, shortest delay and highest reliability, we conduct a statistical analysis on the link state change and the correlation relationship on the shortest path sensitivity to obtain key link indicators. Finally, the actual provincial power communication network is taken as an example to verify the feasibility and correctness of the method. The research conclusion has reference value for the planning, design and operation maintenance of power optical network.