In order to forecast the demand intensity for tourist transit of open expressway service area more accurately, according to the generation principle of tourism intensity, fully considering the influence of three forces including tourists travel demand thrust, tourism cities attraction and travel cost resistance on the strength of tourism, combining gravity model and giving a new meaning to the supply and demand parameters of the prediction model, this paper proposed a new model based on the three interaction forces to predict the demand intensity for tourist transit. In the face of lack of the status quo of tourism data, in order to verify the validity of the model, the method transforming the tourist receipts of tourist city into tourist traffic generation of a particular city was put forward. Finally, in the instance of Shuifu city of Yunnan province, this paper predicted the strength of tourists to travel in Shuifu. Numerical results showed that the model can be calibrated by the instance data and well explain the generation and distribution mechanism of traffic. This work can provide a certain basis for traffic service facilities planning.