Abstract: Tourists' crowding perception and adjustment behavior under crowded condition were explored and the influence mechanism of tourists' crowding-adjustment behavior on tour routes design was analyzed to enhance the tourists' experience and service level of scenic site. "Hot link" was defined and the diversity of tour routes was analyzed according to the popularity and sorting location of "Hot link". Tour routes multi-objective optimization functions were prompted for the tour route design regarding the maximum satisfaction and the minimum walking time between scenic spots and the minimum crowding degree as the optimal objectives. Considering the number of visiting scenic spots, visiting time and other constraint conditions, the goodness value of the tour route was calculated based on the particle swarm optimization model. The impacts of weighed coefficient of crowding degree of scenic spots on tour routes optimization were discussed. A questionnaire of tourists' tour route and behavior information was carried out in the Summer Palace and the optimal tour routes were listed and categorized. Results show that adjustment behaviors such as cognitive adjustment, behavior adjustment and cease adjustment are adaptive to improving tour experience when tourist perceive crowded. The "Hot link" number of quick tour and depth tour is 1-2 and 2-3 respectively. The goodness value of depth tour route (No.75) is 57.39 and is bigger than official recommended tour route, which indicates the optimization model has a higher accuracy. The number, popularity, sorting location and crowding degree value of "Hot link" affect tour routes' goodness value. With the increase of weighed coefficient of crowding degree of scenic spots, some tour routes' goodness value increases, and the recommended sorting changes.