Abstract: Due to the disadvantage of relatively slow convergence and local optimum of basic ant colony algorithm，based on eliminating the influence of the size and dimension of pheromone and heuristic information through standardized transformation，directed pheromone updating on and chaotic selection strategy are proposed to improve ant colony algorithm.Relative location information among nodes in road network is introduced in pheromone updating for higher searching speed，and chaos perturbation is used to improve selection strategy to avoid precocity and stagnation.Then the improved ant colony algorithm is applied in urban traffic dynamic route guidance.The road network of Chongqing Yuzhong Peninsula is taken as an example to calculate the optimal route based on the least travel time，and the experimental results show that this algorithm has much higher capacity of global optimization than basic ant colony algorithm and it is feasible and effective for optimal route choice.