To study the impact of eyelid opening and closing on the volume and morphology of the lacrimal sac using computed tomography (CT) dacryocystography. Method: All of the patients underwent CT dacryocystography. After the contrast agents was injected into a patient's lacrimal sac, the orbit was first scanned with the eye open. And then the patient was told to close the eye firmly for a second scan of the orbit. The volume of the lacrimal sac was calculated by the image processing program which came with the CT machine. At the same time, the anteroposterior and transverse diameters of the lacrimal sac at 3 mm and 7 mm from the top of the lacrimal sac were measured. Results: 14 patients (14 eyes) who met the inclusion criteria were collected between December 2015 and January 2016. The average volume of the lacrimal sac obtained from the calculation based on CT dacryocystography was 0.165 ± 0.073 cm 2 when the eyelid was open and 0.165 ± 0.076 cm 2 when the eyelid was closed, there is no statistical difference. When the eyelid was open or closed, except for the anteroposterior diameter at the upper portion of the lacrimal sac, the differences in the transverse and anteroposterior diameters at the two positions of the lacrimal sac were no statistical difference. Conclusion: When the eyelid is opened or closed, there is no significant change in the lacrimal sac volume or morphology.