Objective To evaluate the clinical diagnostic application and operative efficacy of the expression of NKG2D in peripheral blood CD+8 NKT cell and its ligand sMICA in patients with esophageal or cardiac carcinoma.Methods The peripheral blood NKG2D positive CD+8 NKT cell percentage was concomitantly determined by flow cytometry in 53 preoperative patients including 29 postoperative patients with esophageal or cardiac carcinoma and 30 healthy controls.The serum sMICA was determined by ELISA.Results The peripheral blood NKG2D positive CD+8 NKT cell percentage in patients was significantly lower than that in controls [(77.632±8.972) % vs (89.053±6.515) %] (t = -6.113,P ＜0.05); with stage Ⅱ,Ⅲ,Ⅳ,it decreased significantly in order (F = 99.251,P ＜0.01);with lymph node metastasis lower than that without lymph node metastasis (t = -10.384,P ＜0.01); squamous carcinoma was higher than adenocarcinoma (t =9.899,P ＜0.01); postoperative was significantly higher than preoperative (t =-4.319,P ＜0.01).The level of serum sMICA in patients was significantly higher than that in controls [(326.28±85.407) pg/ml vs (210.00±92.560) pg/ml](t =7.292,P ＜0.01); with stage Ⅱ,Ⅲ,Ⅳ,it increased significautly in order (F =63.355,P ＜0.01); with lymph node metastasis higher than that without lymph node metastasis (t =7.770,P ＜0.01); squamous carcinoma was lower than adenocarcinoma (t =-7.593,P＜0.01); postoperative was significantly lower than preoperative (t =7.027,P ＜0.01).Serum sMICA could inhibit peripheral blood CD+8 NKT cell activation receptor NKG2D (F =142.773,P ＜0.05),determination coefficient R2 = 0.7368.Conclusion The level of peripheral blood CD+8NKT cell activation receptor NKG2D and serum sMICA in patients could be an assistant indicator for