Objective · To investigate dynamic changes in microvessels and partial pressure of oxygen during the occurrence and development of hypertrophic scars. Methods · Patients with early, hypertrophic, regressive, and mature scars were respectively assigned to four groups with 8 patients in one group. Partial pressure of oxygen was percutaneously measured before scar surgery with normal skin as the control. Scar tissues were fixed, sectioned, and H-E stained after surgery. CD34 and hypoxia inducible factor-1 (HIF-1) were measured with immunohistochemistry. Significance analysis was performed on results with two sample mean comparison test (t test). Results · Percutaneous measurement of partial pressure of oxygen found that compared with normal control [(75.3±10.1)mmHg], partial pressure of oxygen started to decrease in early scars [(51.2±8.3) mmHg，P=0.037], further decreased in hypertrophic scars [(30.2±6.1)mmHg，P=0.026], reached the lowest in regressive scars [(6.9±2.1)mmHg，P=0.011], and returned to normal in mature scars [(71.1±9.6) mmHg，P=0.080]. H-E staining revealed that there were a small amount of microvessels in normal skin. Microvessels gradually increased in early scars and reached the highest number in hypertrophic scars. Stenosis or occlusion occurred in most microvessels in regressive scars and microvessels returned to normal in mature scars. Results of CD34 examination further confirmed these changes in microvascular morphology and number. HIF-1 examination found that the HIF-1 expression was low in normal skin, significantly increased in early scars, further increased in hypertrophic scars, significantly decreased in regressive scars, and almost returned to normal in mature scars. Conclusion · There are dynamic changes in microvessels and partial pressure of oxygen during the occurrence and development of hypertrophic scars. These changes are associated with pathological changes in scars and may be mediated by HIF-1.