Abstract: To conquer the disadvantages of low efficiency and the poor practicability of the traditional attack tree, a universal serial attack model and its constructing method were proposed by introducing an order of the atomic attacks. The weights of each tree leave were defined and the effectiveness of the elementary attacks could be quantified. Further, the Dijkstra algorithm was used to calculate the optimal route of the serial attack model, which would offer an optimal attack strategy. Finally, a complex attack tree with twenty leaves was built and analyzed by using the above method. The results indicate that, in comparison with the traditional parallel model, the proposed serial attack tree model with weight concept has the advantages of bigger outcome, lower algorithm complexity, higher efficiency and more perfect effectiveness.