<p>Based on the actual dynamic signal time history measured during revenue services of a railway freight wagon, this study focuses on acquiring the target signal for simulation on the test rig and performing a fatigue test on the accelerated car body. The method used is based on simulating the running conditions of the track. The working principle of the multiple input and multiple output system, along with the TWR iteration progress of the railway freight wagon car body fatigue test rig, is discussed. Additionally, the identifying method and specific iteration workflow of the test system’s frequency response function are provided. Using the C₈₀ type coal-carrying gondola car as a real example, data on coupler load, vibration acceleration, and dynamic stress from a heavy haul special-purpose line are collected. The collected data is then compressed. The test rig actuators create the necessary drive signals for the car body accelerated fatigue test, following the iteration principle, and the fatigue test of the car body is realized. The test results demonstrate that the vibration condition on the indoor test rig replicates that of the actual track. The relative fatigue damage error between the test rig and track measured at the car body stress measuring points ranges from − 0.68 to − 15.58%. The response measured on the test rig aligns closely with the actual measured result, indicating a relatively high simulation accuracy.</p>