This work aimed to study the box pallet size suitable for railway boxcars, in order to promote the containerization of railway and seek for the optimal goodness of fit between the railway boxcars and the containers. First, the loading efficiency of the three kinds of common pallets in the society by five kinds of railway boxcars was calculated, and then the box pallet size with the highest loading efficiency was chosen for the railway boxcars based on the pallet of 1200 mm×1000 mm using the hierarchical optimization algorithm. Analysis of the loading efficiency of railway boxcars showed that the loading efficiency of 1200 mm×1000 mm pallet by all five boxcars (P50， P60， P61， P64， P70) was above 82%, and the loading efficiency was stable. For the P50， P60， P61， P64 types of boxcars, the 1200 mm×1000 mm×760 mm box pallet had the highest loading efficiency, while for P70, the loading efficiency of all types of box pallets was similar. The box pallet size of 1200 mm×1000 mm×760 mm was the most efficient tray for railway boxcars.