Objective To investigate the clinical features of interface fluid at an early stage after partial lamellar keratoplasty （LKP） and observe the therapeutic effect of releasing interface fluid. Methods This was a retrospective， noncomparative clinical trial. Thirty-eight patients with onset of interface fluid were identified among 433 patients who underwent partial LKP at Shandong Eye Hospital from September 2007 to January 2011. Examinations were conducted 2 to 4 hours after surgery. The primary disease， the preservation of donor corneal tissue， and the size difference between the corneal graft and the recipient bed of the patients with interface fluid were assessed. The interface fluid was released immediately under a microscope， and the effect was evaluated. Data were analyzed using x2 test. Results Interface fluid was found in 38 cases （8.8%） at 2 to 4 hours after LKP， including 18 cases of keratoconus， which was significantly more than the other diseases. The rate of interface fluid in patients whose donor corneas were preserved in glycerin （10.4%） was higher than the rate in donor tissue preserved in a DX solution （4.3%， x2=4.060， P＜0.05）. The rate of interface fluid in donor tissue preserved in glycerin more than 3 years （17.7%） was higher than that preserved for less than 3 years （9.3%， x2=12.152， P＜0.01）. Corneal grafts 0.5 mm or larger than the recipient bed induced more interface fluid （19.5%） than those 0.25 mm or larger （7.7%， x2=6.521， P＜0.05）. The graft and recipient bed attached tightly after the fluid was released， and regained transparency 1 week later. However， a large amount of interface fluid was found in 1 patient the day after LKP. The recipient tissue reflexed inward and attached to the anterior lens capsule. There was pupillary block combined with high intraocular pressure. Releasing the fluid alone could not restore the anterior chamber so peripheral iridectomy was performed. The intraocular pressure became normal after surgery， and the edema was absorbed by 1 week. Conclusion Interface fluid after partial LKP is closely related to keratoconus. Long-term glycerin preservation of corneal donors and excessive oppression of the graft to the recipient bed are also predisposing factors for interface fluid. It is important to check with slit lamp during the early stage after surgery. Immediate release of interface fluid is an effective method to avoid serious complications.