Objective To clarify that the vascular endothelial cell injury caused by obstructive sleep apnoea hypopnea syndrome (OSAHS) is partly mediated by miRNA-92a. Methods Serum miRNA-92a level was measured in patients who underwent polysomnography between January 2018 and December 2018. The correlation between miRNA-92a and OSAHS was analyzed. Meanwhile, endothelial cells were cultured in vitro, and morphological changes and JC-1 staining results of endothelial cells were observed after OSAHS serum stimulation, so as to further clarify the injury of endothelial cells. The changes of miRNA-92a target gene were detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot to further clarify the mechanism of endothelial cell injury. Results Seventy-two patients received polysomnography, including 22 cases in the non-OSAHS group, 18 in the mild OSAHS group, 10 in the moderate OSAHS group, and 22 in the severe OSAHS group. Serum miRNA-92a level was significantly increased in the OSAHS patients, and it also increased with the aggravation of OSAHS severity. OSAHS serum significantly damaged endothelial cells. Endothelial cells were swollen, disordered arrangement, and unclear boundaries. JC-1 staining showed that green fluorescence was significantly enhanced compared with the control group. RT-PCR and Western blot showed that the expressions of Krüppel-like factor-2 (KLF-2), Krüppel-like factor-4 (KLF-4) and endothelial nitric oxide synthase (eNOS) were significantly decreased under OSAHS serum stimulation. Conclusion Serum miRNA-92a of OSAHS patients is significantly increased, and reduces the expression of target genes KLF-2, KLF-4 and eNOS, affects the mitochondrial function of endothelial cells, and injures endothelial cells.