Objective To explore the effect of Fas, Fas ligand (FasL), soluble Fas (sFas) and their clinical significance in KD. Methods The expression of Fas, FasL in peripheral blood lymphocytes (PBLC) were detected with flow cytometery at acute and remission stages in patients with KD; and the serums Fas was detected by double antibody sandwich ELISA in the patients with KD at acute and remission stage, meanwhile erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) were also tested. Results The expression of Fas, FasL in PBLC in patients with KD at acute stage was (14.2±0.5)% and (1.61±0.09)% respectively , which were significantly lower than those at remission stage [(15.7±0.5)%, (1.95±0.09)% respectively (P<0.05 and P<0.01)]. The expression of Fas in PBLC in the patients with KD at acute and remission stage was both significantly lower than that in normal control group (20.8±0.5)% (P<0.01 both);The expression of FasL in PBLC in patients with KD at acute and remission stage was both significantly lower than that in normal control group (20.8±0.5)% (P<0.01 both); the serum sFas in patients with KD at acute and remission stage was (1906±55)μg/L and (1622±52)μg/L respectively , which was significantly higher than that in normal control group (1151±51)μg/L (P<0.01 both); the serum sFas at acute stage was obviously higher than that at remission stage (P<0.01); there was positive correlation between sFas and ESR, CRP (P<0.01 both). Conclusion There are abnormal expressions of Fas/FasL in PBLC and sFas in patients with KD. Fas/FasL is lower and sFas is higher than that of the controls. The abnormal expression of Fas/ FasL in lymphocytes and the apoptosis triggered by sFas are probably involved in the immunological aberrance and pathogenesis of KD. sFas may be used as a marker to evaluate the disease activity and therapeutic efficacy.