In view of the premature convergence problem of the basic Ant Colony Optimization Algorithm, the basic ant colony algorithm was improved through the introduction of information entropy and the improvement of parameter τ , and the improved ant colony algorithm was used to find the structure of the weakest failure path.On the basis of the geometrical meaning of structural reliability index, the problem of structural reliability index was converted to the corresponding unconstrained optimization problem by use of the penalty function method, and then the Particle Swarm Optimization algorithm was used to calculate the structural reliability index.Taking 10-bar truss for example.its reliability index calculation was compared respectively by means of response surface method, the improved ge· netie algorithm and this algorithm.it is concluded that particle swarm algorithm and ant colony algo。 rithm has high convergent rapid and high precision for solving reliability index.