A finite element model was developed to study the transient propagation behavior of multi rail cracks under the transient wheelrail rolling contact loads.The influences of the transient rollingsliding behavior on the load boundary of the cracks and the contact between crack faces are considered in the developed model,which breaks through the limitations of the assumption of the steadystate rolling contact boundary based on Hertz theory widely employed in the previous studies.In light of the actual measurements,the angle of cracks was set to be a typical value of 30°,the length and depth were taken as 10 to 20 mm and 2 to 4 mm,respectively (a fix ratio of 5 between the length and the depth),the crack space was taken as 5 to 20 mm in the model,the stress intensity factors at the crack tip under the condition of coexistence of up to 5 cracks were analyzed at running speed of 300 km/h.Results show that with respect to the single crack case,the interaction between multi cracks reduces the the nodal forces at the crack tip,while increases the relative displacement between the crack faces near the tip,and consequently,leads to higher stress intensity factors.For parallel cracks of 15 mm long (the same sizes assumed for each crack),their interactions can be captured accurately by a 3 crack model when the crack spacing is greater than 5 mm,whose error is only 1.7% with respect to that of a 5 crack model.For the multiple cracks studied in this paper,the interaction between cracks can be ignored when the crack spacing is greater than the crack length,so a single crack model can provide sufficient accuracy.