The curve negotiation ability and lateral stability are the important and contradictory indicators when evaluating the dynamic performance of the rail vehicle. And in order to study the stability of the rail vehicle, its curve negotiation ability will be studied firstly. In this paper, the whole multi-body dynamic model of the rail vehicle was proposed based on the theory of multi-body dynamics in the software of Simpack. And the lateral force, derailment and overturning coefficient of the rail vehicle when it passed through a specific curve track with specific speed. Then the curve negotiation ability of the rail vehicle was estimated accurately.