It is important for non-invasive measurement of arterial stiffness to set a pressure sensor on the center of artery. In previous our study, moving the reflection optical sensor on an inner side of wrist, we observed inversion phenomena that a dicrotic wave and a percussion wave of reflection photoplethysmography (incident wavelength of 530, 650 and 810nm) were turned over. If the relationship between inversion phenomena and a location of artery is clarified, we expect that inversion phenomena will be applied to use an artery detection system. The purpose of this study is to clarify the mechanism of inversion phenomena, and to suggest the artery searching method by using inversion phenomena. In this study, we investigate the mechanism of inversion phenomena by a measurement of pulse wave using the reflection optical sensor and a numerical analysis of light propagation in a wrist, and examined this method to estimate a artery position by this measurement. Numerical analysis results indicated the cause of inversion phenomena is influence of scattering. In the results of measurement, inversion phenomena occur under the optical sensor setting on the center of artery. In conclusion, it is available for an artery searching method to use reflection photoplethysmography of incident wavelength 530nm and 810nm.