Rail vehicle is a multi-input and multi-output system. When the system has m inputs and n outputs, there are m frequency response functions corresponding to the output of each coordinate, and the whole system has A total of m×n frequency response functions It is required to solve the vehicle response to solve all H(ω), which is more complicated than the above one or two H(ω), but the idea of solving the problem is the same. The transverse random vibration is caused by the random excitation of the track when the rail vehicle is running, which has the property of forced vibration. When the amplitude of the track direction irregularity is obviously greater than the wheel-rail clearance, the intense vibration of the rim hitting the rail will be produced, which is different from the wheel-set instability snake motion described below. When running below the critical speed of hunting instability, the hunting motion of the rail vehicle on the ideal straight track is gradually attenuated. The formation mechanism of horizontal force and vertical force between running, guiding wheel and magnetic wheel and track is also different with different running parts, which will be introduced. The last is an overview of the common response characteristics of ordinary rail cars, and the CR400AF is taken as an example.