The spring constant method is a newly proposed method to evaluate the arterial stiffness. However, whether the spring constants computed using the radial pulse and photoplethysmography (PPG) show a similar characteristic deserves to be investigated. The experimental group comprised 40 participants (18 men and 22 women), all with diabetes mellitus and ranging between 48 and 75 years of age. All were subjected to the measurements of the radial pulse and PPG pulse. Parameters, the amplitude, the rising slope, the second derivative of the peak and the spring constant of the two types of pulses, were used for analysis. Statistical results showed that only the spring constant parameter revealed the significant relationship (correlation coefficient = 0.78, p <0.001) between the radial pulse and PPG pulse. In other words, regarding to the assessment of arterial stiffness, the radial pulse and PPG pulse showed a similar characteristic. The finding provides more alternatives to evaluate the arterial stiffness in clinic.