To measure the cooperation effect between civil aviation and high-speed rail, the paper quantifies the impact of the hub integration between airports and high-speed rail stations on airport passenger throughput and proposes a hub-integrated model based on the difference in differences method. Airports in China mainland with complete annual passenger throughput from 2007 to 2018 are selected into the sample. And for the requirements of the non-randomized controlled trial, those which integrate with stations are divided into the treated group and the rest are in the control group. Then a balanced panel dataset about all chosen airports and the cities where those are located is created for econometric analysis. To control the influence of confounding factors and satisfy the parallel trend assumption which is the basic condition of the difference in differences method application, propensity score matching is carried out by using the nearest neighbour matching within a caliper. Results show that the annual passenger throughput of the treated airports increases by 17.5% on average than before. Since most of the new airport passengers are transferred to or from high-speed rail stations, it is beneficial for both transport modes to construct the hub integration.