BACKGROUND: To present the iridectomy combined with posterior approach anterior chamber gas injection technique for the treatment of extensive Descemet's membrane detachment (DMD), which is a novel surgical approach for the management of DMD after phacoemulsification. CASE PRESENTATION: The surgical technique was performed on a 68-year-old female with a history of cataract phacoemulsification surgery and two times of anterior chamber gas injection to treat DMD. After creating a scleral tunnel at 4 o'clock of the limbus, the iris root in that direction was cut off. This was confirmed via an iris root incision indicating that the syringe needle entered the posterior chamber through the scleral tunnel. The anterior chamber was filled about 3/4 with 16% C3F8. After surgery, patients were required to maintain a supine position without pillows. One month post-surgery, the cornea was transparent, DMD had fully recovered, and the best corrected visual acuity improved to 20/20. CONCLUSIONS: The iridectomy combined with a posterior approach anterior chamber gas injection technique can be used as an alternative surgical option for the management of extensive DMD in patients who have undergone several ineffective anterior chamber gas injection surgeries.