The base design of core equipment of nitric acid 4 in 1 set relates to the life span and stable safety operation of units in the nitric acid production process. Through the transient dynamics analysis, it can be inferred that the change of the nitric acid 4 in 1 machine set base in the start-up phase and stable operation phase over time, and finding out the larger amplitudes parts. It was pointed out that increasing the length and the width of the unit base, in the start-up stage of the turbine when the speed is 900,2 300,4 400,6 200 and 9 520 r/min，the displacement of dynamic response meets the design requirements. The designed unit has put into use,running in good condition,and the vibration phenomenon during the start-up stage is clearly improved.