Objective To know the establishment of the flap pedicle blood supply and the right moment of the cutting off of pedicle by means of laser Doppler blood perfusion imaging instrument on the random flap blood flow changes.Methods 20 adult healthy rabbits were divided in to four groups and each 5 have unilateral flaps.1,3,5,7,9,12,14,18 days after operation,the pedicle blood perfusion values (PU) measurement of the distal pedicle on the flap and midpoint of both ends of the pedicle were performed,and PU values were analyzed.Results Pedicle of the PU values at the different time points changed little (P＞0.05).The PU value in the distal flap reached the minimum 1 day after operation and then increased gradually [3 d (1.24±0.07),5 d (1.57±0.15),7 d (1.79±0.08),9 d(1.89±0.13),12 d(2.01±0.16),14 d(2.18±0.09) and 18 d(2.40±0.18),P＜0.05].When distal PU values/pedicle PU value≥1.2,the flap survival rate reached 99%.Conclusions The establishment of random skin flap blood circulation,as well as the ratio of PU values of distal to the pedicle flap pedicle can be used as the timing of an important indicators.