A 3D wheel-rail rolling contact fatigue cracks propagation model with wheel polygon was developed by ANSYS/LS-DYNA.By considering the transient rolling-sliding and high-frequency dynamic effects between the actual wheel and rail,the effect of transient contact load caused by wheel polygon and continuous cracks on the dynamic propagation behavior of rail cracks was analyzed.The results of traction condition at a speed of 250 km/h show that the no-gap multiple cracks have little effect on the normal force,but cause non-negligible fluctuations in the tangential force.The wheel polygon will cause significant periodic fluctuations in the normal and tangential wheel-rail forces.For example,23-order polygon with the deep of 0.1 mm will increase the maximum normal and tangential contact forces of each crack surface by 19.6% and 34.1% respectively compared with the smooth wheel condition.The contact stresses in crack surfaces have complex transient changes within 0.22 ms of the contact patch running,which further causes the periodic fluctuation of the maximum crack tip stress intensity factor of each crack and affects the dynamic propagation behavior of cracks.With the increase of the depth and order of the wheel polygon,the amplitude of the above-mentioned various fluctuations will become larger,and the crack propagation will be accelerated.