Aiming at the disadvantage that basic dolphin swarm algorithm is easy to fall into local optimum, an improved dolphin swarm algorithm based on information entropy is proposed. The algorithm measures the uncertainty of dolphin swarm search phase by information entropy, controls the selection probability of search phase, reduces blind search, and overcomes the shortcomings of local optimum and premature convergence in the search phase of basic dolphin swarm algorithm. The improved algorithm is applied to the optimization of truss structure and compared with other algorithms. It is proved that the improved algorithm has better performance in convergence speed and optimization accuracy. It is applied to optimum design of truss structure, and provides an effective method for optimum design of structure.