In general, it is not easy to detect the foot of the pulse wave because the systolic and diastolic waveforms of the pulse wave change every moment due to various factors such as thecharacteristics of the blood vessel wall, viscosity of the blood, influence reflected in the pulse wave, proper vibration of tissue in the artery system, etc. The characteristic point of the pulse wave should reflect the beginning point of the pulse wave, and should not be influenced by the transmission characteristic of the blood vessel and the frequency distortion. For this reason, the characteristic point of the pulse wave to minimize the calculation error generating from the form change of the pulse wave was detected in most researches on the PTT calculation.The characteristic points of the pulse wave generally used are the maximum, the minimum, the average point between the maximum and the minimum of pulse wave signal (RM50), the maximum of first derivative and the maximum of the second derivative of the pulse wave, the intersection of a line tangent, and the intersection of two line tangents. In this study, the maximum point of the second derivative of the pulse wave providing noise resistance, the stable result and easyimplementation was used as the characteristic point of the pulse wave for the calculation of PTT.