Abstract: Objective：To investigate the correlation between the diameter size of communicating vein and chronic ulcer of lower extremities.Methods：Retrospectively analyse the datas of 60 cases with venous ulcers of lower extremities which were received and cured in authors,hospital from Jan.2016 to Jan.2020.Put them into observation group.The other 60 cases with physical examination at outpatient department are put into control group.All the patients in two groups have a color Doppler ultrasonography examination in the veins of lower extremity.The diameter sizes of communicating veins in two group were measured and recorded.Result：The average reflus time of communicating vein in the observation group is more than 0.5 second.The average reflus time of communicating vein in the matched group is less than 0.35 second.The mean diameter size of communicating vein in observation group is morn than 4 millimeters.The mean diameter size of communicating vein in matched group is less than 3.3mm.Conclusion：When the diameter communicating vein size is more than 4mm,Chronic ulcer will be found in the lower extremities.

Key words: venous ulcer, communicating veins, extremities, venous incompetence