Objective To assess the clinical application value of phleboplasties combined with microvascular anastomotic device in venous anastomosis with diameter discrepancy in head and neck defects reconstruction.Methods Sixty-six pairs of veins with significant diameter discrepancy were anastomosed in head and neck reconstructive surgeries with free flaps.Forty of them were anastomosed with microvascular anastomotic device (the coupler group) after phleboplasties including lateral incision, Y-T enlargement and wedge excision while the other 26 pairs of veins were conventionally sutured (the sutured group).Diameter of each vein, anastomosis time, post-operative vascular crisis, flap survival and complications related to the microvascular anastomotic device were recorded.Results The average anastomosis time of the coupler group was (4.78 ± 1.14) min for lateral incision, (5.16 ± 2.07) min for Y-T enlargement and (11.09 ± 3.21) min for wedge excision, and all of them were significantly shorter than that of the sutured group.In the sutured group, all flaps survived except for 2 veins with poor blood flow were cut and re-anastomosed during the operation;1 flap with venous crisis within 72 hours after the operations was explored and replaced with the pectoralis major myocutaneous flap.All veins in the coupler group were successfully anastomosed in a single coupling procedure without anastomotic impatency, blood leak, vessel tearing and ring shedding.No vascular crisis occurred postoperatively.One patient underwent cervical haematoma 5 hours after the operation, and the flap blood supply was unaffected after the haematoma was removed.All flaps in the coupler group survived completely.Patients in both two groups were followed up 6 to 18 months.All flaps healed perfectly and no obvious surgical complications or microvascular anastomotic device rejection happened.Conclusion When anastomoses are carried out using microvascular anastomotic device between veins of different size, phleboplasties including lateral incision., Y-T enlargement and wedge excision can not only reduce the size discrepancy and the anastomosis time, but also ease the difficulty level and guarantee the patency of the venous anastomoses.Wedge excision enjoys the advantage of haemodynamics, and obstruction of venous reflux hardly occurred for size reduction.It should be considered preferentially when external jugular veins are used as the anastomotic vein of the recipient sites in head and neck reconstruction.