Abstract： 【Objective】To investigate the character of expression of NK cells and its receptors in peripheral blood of pa? tients with HBV-related acute-on-chronic liver failure（HBV-ACLF）in different phase.【Methods】There are thirteen pa? tients with HBV-ACLF in advanced phase group and thirty-three patients in plateau phase group，with thirteen healthy per? son in control group. The frequency of NK cells and expression of NK cell activating receptors（NKAR）including NKG2D， NKp30 and NKp46，NK cell inhibitory receptors（NKIR））cludingsd ate the character of including NKG2A，KIR2DL1， KIR2DL3 and KIR3DL1，NK cell killing function related factors including Perforin，GranzymeB and FasL in peripheral blood of all patients were detected by flow cytometry.【Results】The percentage of NK cells in advanced group was lower than plateau group and healthy control group（H=7.771，P=0.021）. The expression of KIR3DL1 in healthy control group was high? er than advanced group and plateau group（Z=6.639，P=0.036）while the expression of FasL was significantly lower than ad? vanced group and plateau group（Z=22.5，P<0.001）.【Conclusion】Patients in advanced group had lower frequency of NK cells，lower expression of inhibitory receptor KIR3DL1 and higher expression of FasL than patients in plateau group and healthy control group，which is associated with immune status of patients in different phase of liver failure.