Based on the dynamic simulation model, the dynamic response index of vehicle system under the action of track irregularity is divided into three areas: repair, deterioration and maintenance. The correlation between the track irregularity index and the dynamic response index domain of vehicle system components is calculated and statistically studied. The estimation model of dynamic response index domain of vehicle system and the domain boundaries of different dynamic response indexes are established and obtained Line. According to the principle of single variable method, the excitation source of vehicle track system is divided into track irregularity and other comprehensive factors (such as temperature load, material damage, etc.), and a simple inversion method of track foundation state is proposed based on the estimation model of dynamic response index domain. Its basic principle is: if the statistical characteristics of track irregularity remain unchanged and other influencing factors change, the estimation domain and measurement domain of dynamic response index will produce grade jump, so as to determine whether the basic state of the line is normal. The simulation results show that the accuracy of domain estimation of dynamic response index of vehicle system is more than 80%, and the accuracy of recognition is more than 70% for the damage condition of the line infrastructure, where the fastener is empty.