Abstract: For the problem that the hard disk can’t read in the vibration test of a ruggedized computer, through the modal and harmonic response analysis by the finite element software, combined with the measured data, the cause of failure is as follows: insufficient rigidity of the motherboard triggers resonance and then disables the hard disk to read. After the structural improvement, the motherboard no longer resonates, the failure no longer occurs during the prototype test and the acceleration of the test point is significantly reduced. Anti-vibration design method of the printed circuit board (PCB) of the ruggedized computer is further explored. By approximate calculation of the natural frequency of PCB according to thickness and fastening screw spacing, several sets of design values of the thickness and fastening screw spacing are obtained that canbe widely applied to the printed circuit board of ruggedized computer.