Abstract: Based on microscopic simulation,drivers' day-to-day route choice behavior and evolution of network flow under forecast information are investigated.First,current reports hardly research drivers' day-to-day route choice under forecast information.A feasible travel time prediction method is designed.A model updating the drivers' perceived travel time and a route choice model are developed according to the drivers' day-to-day route choice process.Then,by establishing a simple road network with two parallel routes,the drivers' day-to-day route choice is simulated under forecast information.The fluctuation of route flow and efficiency of the system are analyzed when the parameters take different values.Results show that the fluctuation of network flow and efficiency of network are both related to drivers' reliance on the information and forecast model's parameters.Moreover,their changes are similar.Finally,the parameter's optimal range is obtained.