Water-dispersive upconversion nanoparticles(UC@PEI NPs) were synthesized by hydrothermal method using polyethyleneimine(PEI) as surface modification agent. The effects of solvent components, reaction time, PEI molecular weight and addition amount on luminescence intensity were investigated and characterized. The results showed that the optimal synthesis conditions were V(H2O):V(EG) = 1:1, PEI(Mw = 10000) was added 1.2 g, and reacted at 200 ℃ for 8 h. Subsequently, in the presence of UC@PEI NPs and poly(N-isopropylacrylamide)(PNIPAM), acrylamide, N,N'-methylenebisacrylamide were copolymer-ized by free radical polymerization to prepare composite hydrogel. The morphology, mechanical strength and luminescent thermo-sensitive were characterized by SEM, tensile testing machine and luminescence spectrometer. The results showed that composite hydrogel with the interpenetrating network structure still remained intact after repeated dehydration and swelling, and the average dehydration ratio and swelling ratio were 81.18% and 61.38%; the strain under stress was 251.10%, and the mechanical strength was 38.09 kPa; under the excitation of 980 nm NIR laser, the luminescence intensity at 540 nm(Er3+, 4S3/2 → 4I15/2) decreases by 42.64% when the temperature rises from 20 ℃ to 48 ℃, and the luminescence intensity can be reversibly recovered when the temperature decreases. This shows that the composite hydrogel has the properties of reversible upconversion luminescent thermo-sensitive, good material stability, good stretchability, and has a certain mechanical strength.