In order to improve the efficiency of path calculation and the dissimilar of planning paths of K-short path(KSP) algorithm. First, this paper introduces the graph theory description of optical network, definition of path similarity and parallel edges theory. Then it describes the KSP problem and the traditional Yen algorithm briefly, and analyzes the research status of KSP algorithm. Finally, the paper proposes an Yen improved algorithm, and expounds the calculation strategy of dissimilar paths and the implementation steps of the improved algorithm emphatically. By constructing a topology map similar to the actual production environment, the Yen improved algorithm is verified, and the path proximity and calculation speed are compared with other algorithms to prove its effectiveness.