Aiming at the outstanding problem of low connection reliability of the air-rail intermodal connection plans, this paper studies the air-rail timetable optimal coordination problem, in order to provide passengers with coordinated, efficient and reliable travel plans. This paper analyzes the probability distribution of flight delays according to historical flight operation data; based on the existing connection relationship between flights and trains, takes adjusting the train timetable as the optimization strategy, and establishes a model with the objective of minimizing the connection time and maximizing the reliability of connection plans. Shijiazhuang Zhengding Airport is taken as the research object, and validity of the model is verified. Impact of adjusting train timetable on improving the reliability of connection plans while meeting connection time requirements is summarized and analyzed, and suggestions for air-rail intermodal products design are proposed.