A user-experience-based handoff decision method towards Integrated Satellite and Terrestrial Network (ISTN) is proposed to guarantee the user session continuously. It selects the network with the lowest user experience difference, so each user can access to the most appropriate network. Meantime, a speed perception module is designed based on fuzzy method for the purpose of decreasing handoff times with high mobility. Simulation performance proves the superiority in reducing the probability of handoff failure and new call blocking. Moreover, the system can maintain a higher average network load to serve more users, which indicates the superiority of resource allocation among the whole network.