In order to study collision response of trains with different train lengths, a one-dimension longitudinal collision simulation platform is established based on the Zhai method. The one-dimensional longitudinal collision simulation platform is validated by comparing impact responses of the same train grouping, such as speed and energy, with results of the one-dimension longitudinal collision simulation platform. On the basis of this platform, the collision responses of active and passive trains under the same and different train setting conditions are studied by taking the speed, acceleration and absorbed energy of the vehicle as the indexes. The results demonstrate that when the train setting length of the active vehicle is the same, the velocity at the end of the collision will decrease with increased train setting length, and the energy absorption ratio will increase with increased train setting length. When the length of the active vehicle is longer than that of the passive vehicle, the energy absorbed by the collision is less and the remaining kinetic energy is larger, thus meaning that the collision will be more dangerous.