Abstract: Releasing travel information to guide travelers'travel choice is an effective way to relieve traffic conges-tion .In order to describe the influence mechanism between road congestion extent and travelers'route choice decisions , the cumulative prospect theory is used to model travelers'decision-making process ,and the travelers'different congestion cognitive model s and congestion information demand are analyzed .The concept of road network congestion threshold is analyzed ,and the calculation model of road network congestion threshold is constructed based on Cumulative Prospect Theory (CPT) with travel time as decision index .In the numerical example part ,travelers congestion cognition and travel decisions are modeled with a simple road network .The result of numerical example reveals congestion threshold's influ-ence on route choice decisions ,and verifies that the congestion threshold is the cut-off point of decision change in travelers'decision-making process .Travelers will not change route when travel time is within congestion threshold ;when travel time exceeds the congestion threshold ,traveler will choose another route to travel .