This paper presents a new method for obtaining the noninvasive and unrestrained blood pressure readings noninvasively and unrestrainedly using based on reflected wave arrival time(RAT) in the volume of pulse. Since this new method employs only volume pulse, is more rapider and simpler than the method using pulse transit time(PTT) because it only employs the volume of pulse. Blood pressure, PTT and RAT were acquired from 15 healthy subjects. Each subjects were performed forty trials of each measurement. As a result of those trials, the mean error between oscillometric and RAT measurements for systolic blood pressure was $4.55pm5.64mmHg$. This result showed quite equal with the mean error between oscillometric and PPT measurf:ments, $4.22pm5.30mmHg$, However, it was not obtained a satisfactory result in the relativity of oscillometric to both RAT and PPT measurements for diastolic blood pressure because of personal difference. To conclude, the method of systolic blood pressure estimation noninvasively and unrestrainedly using by RAT may be used as the method by PTT. Nevertheless, additional studies would be necessary for the RAT/PTT estimation of diastolic blood Pressure measurement.