Objective:To investigate the relationship between gap width(GW) and actual defect length(ADL) of femoral artery and vein. Methods:The influence of actual isolated length(ACIL) on GW was investigated in section A. Twenty-four femoral arteries (veins) in 12 rabbits were randomly divided into three groups. A range of 15.0mm, 25.0mm and 35.0mm of artery(vein) was isolated from peri-vascular connective tissues(including femoral nerve and vein) and arterial (venous) brallches respectively to clear off longitudinal vascular tedlering in different groups. Apparent isolated lengh (ApIL), increased isolated lengal (IIL) and GW were measured after the artery was transected at its middle portion and stretch ratio(λ) was caculated. The influence of ADL on GW was investigated in section B. Eighteen femoral arteries (veins) in nine rabbits were randomly divided into three groups (AcIL=35.00mm). A segment of 5.0mm, 15.0mm and 25.0mm long arteries (veins) at physiological tension was resected respectively. ApIL. IIL and GW were measured. Results:IIL and λ were unchallgeable while a linear relationship existed between GW and AcIL (GW=AcIL· (1 -1/λ) in statistics in section A. In section B, ADL didn't influence ApIL and IIL but increased GW linealy (ΔGW=ΔADL/λ) in statistics. Conclusion: An adaptive relationship may exist between GW, AcIL and ADL within 35.0mm AcIL range of rabbit's femoral vessel: ADL=AcIL- (AcIL+IIL- GW)·λ orADL= (ApIL-IIL)-(ApIL - GW)·λ. (λa=1.58, λv = 1.64, IILa= 3.85mm, IILv= 3.39mm).