Heart rate variability (HRV) and pulse rate variability (PRV) have been widely used as an automatic nervous system (ANS) activities observation. Based on the timescale limitation of heart beat (for HRV) and pulse waveform (for PRV), one method of instantaneous pulse rate variability (iPRV) with photoplethysmography (PPG) had been proposed as a HRV and PRV surrogate during non-stationary condition in frequency domain. In this paper, the examination in time-domain PPG during passive leg raise (PLR) trial was studied. The 24 subjects pre-experiment resulted that iPRV and HRV are positive correlation (r-value = 0.680±0.099 in baseline; r-value = 0.688±0.096 in PLR). Furthermore, the iPRV containing much complex intrinsic components on higher frequency bands provides more intrinsic cardiovascular information for further assessment. This proposed examination in time-domain PPG is the possible leading way to more useful indicator for healthcare application.