In order to understand the generation of rail oblique crack, based on vehicle-track coupling dynamics theory, the coupling dynamics system with vehicle, rail, sleeper and roadbed was constructed. By using new fast explicit numerical integration method, movement differential equations of system were solved, and wheel-rail forces and contact geometry relation were obtained when power car crossing curve track. Results of calculation have shown that when power car is crossing curve track, lateral forces of outer rail at all wheelsets are pointed to outer rail, longitudinal forces are pointed to forward direction of wheelsets, and their resultant forces are pointed to the second quadrant. Wheel-rail contact points of outer rail at the first and third wheelset are located within 13mm radius of railhead, but at the second and fourth wheelset they are located within 80mm radius of railhead. Degree of wheel-rail interaction at the first and third wheelset is severer than that at the second and fourth wheelset. According to direction of resultant forces and location of wheel-rail contact points, it can be learnt that greater wheel-rail force at the first and third wheelset will easily cause generation and growth of rail oblique crack when power car crossing curve track.