Predicting the dynamic behavior of train collisions using similitude theory is a valuable design tool. However, several limitations and difficulties persist when designing a similar train model. This study proposes a mechanical equivalence similitude method when a train crashes into a rigid obstacle longitudinally, which can be used to establish similitude laws and predict the dynamic responses of a full-scale high-speed train middle vehicle. This method includes impact force equivalence (IFE) and finite-element stiffness equivalence (FESE). The aim is to overcome the insufficient accuracy of establishing a similar train model using traditional similitude methods. First, the similitude laws of the end energy absorber and the vehicle body were deduced. Subsequently, the 1/8th equivalent similar middle vehicle model of the high-speed train was established. The IFE method was employed to design a 1/8th equivalent similar model of the end energy absorber. Based on the FESE method, a 1/8th equivalent similar model of the middle vehicle body was built. Finally, the accuracy and effectiveness of a similar train model were validated through numerical simulations and tests. Comparing the results of the prototype, the errors of the dynamic responses were less than 4%, indicating that the mechanical response equivalence similitude method is effective for constructing a similar train model.