Abstract: Railway passengers waiting time distribution (WTD) is theoretical basis for studying passengers'distribution characteristic. Passengers waiting time at Beijing south station shows a positive correlation between the average waiting time and the train operation distance. Train operation distances were divided into seven groups according to different distances. Each group was fitted with lognormal distribution function, and revealed parameters μ and σ obey respectively linear and logarithm functional relationship with train operation distance l. Then, based on train operation distance, an improved passengers WTD function g(t)=ξ(l) was established. The model was applied in forecasting the number of passengers arriving at waiting rooms. The results reflected the otherness of train operation distances could provide a theoretical basis for optimizing the railway passengers' arrivingstrength.