To improve the alignment in the old road reconstruction project，stress analysis was carried out，and the alignment and smoothness parameters were used as the major variables in the dynamic equation.A “human-vehicle-road ” dynamic analysis model was established，and alignment comparison groups were set，with only one group set with easing vertical curves.The Newmark- β method was used for programming and calculating the dynamic effects generated by the basic alignment with a radius of 7 000 m.The vibration indicators such as peak acceleration，root mean square of acceleration，vibration period，and frequency were used to analyze the dynamic effects of the basic alignment group.By analyzing the causes and decay rules of the vibration zone，the vibration zone and stable zone within the alignment were defined.The addition of easing vertical curves significantly changed the vibration mode of the vehicle，greatly reducing the peak acceleration and root mean square of acceleration to 5% within the conventional basic alignment and effectively eliminating the perception of vehicle vibration.The influence of vehicle type，vehicle weight，and suspension system parameters on the dynamic effects of the two alignment groups was analyzed.The addition of easing vertical curves greatly reduced the vibration，making the alignment more adaptable to various vehicles.The coupling effect between the alignment groups and different smoothness application states was analyzed.The coupling effect of the conventional basic alignment in the vibration zone was more significant，with the root mean square of acceleration being 95%?161% that of the straight slope shape.After adding easing vertical curves，the coupling coefficient approached 1，and the alignment was close to the ideal plane of the “human-vehicle-road ” system.Through the above research，it is found that adding easing vertical curves can effectively improve the vehicle running quality of the alignment and enhance its adaptability to vehicles and road conditions.