Abstract: In order to reduce the deviation caused by subjective randomness, the maximum difference scaling (MaxDiff) method is introduced to carry out the subjective evaluation test of sitting human discomfort under mechanical impact, and the comfort is evaluated by objective indexes combining the acceleration and inertia force. Sixteen mechanical shocks with different nominal frequencies or displacement amplitudes were reconstructed. The subjective scores of 12 subjects under different mechanical impact signals were obtained using the MaxDiff method. The acceleration sensor and the force plate are used to obtain the objective data, so as to extract the peak value, peak to peak value, vibration dose value (VDV), maximum transient vibration value (MTVV) and other objective evaluation indexes. The correlation analysis and linear regression fitting are used to analyze the subjective and objective correlation. MaxDiff scores show that with the increase of nominal frequency and displacement amplitude of mechanical impact signal, human comfort becomes worse. Correlation analysis shows that there is a great correlation between subjective score and objective indexes. Except for the VDV, the correlation coefficients of objective indexes and subjective score are all around 0.9. The linear fitting regression results show that the peak value, peak to peak value and MTVV of acceleration and inertia force can be used as objective indexes to characterize the comfort of sitting human body under impact conditions, with the former being more suitable.