This paper details the study of La2O3 modifications and their effect on the stability of a NiO–CaO/Al2O3 sorption complex catalyst used in the ReSER (reactive sorption enhanced reforming) process of hydrogen production. The La2O3-modified NiO–CaO/Al2O3 sorption complex catalyst was prepared by isometric impregnation. The microstructure, morphology and reducibility of the La2O3-modified sorption complex catalyst were characterized by means of BET, TEM, XRD and TPR. The stability of the catalyst used in the ReSER process was evaluated on a laboratory-scale fixed-bed reactor. Our results showed that modifying the sorption complex catalyst with La2O3 improved its stability up to 30 cycles of the ReSER process for hydrogen production, while only seven cycles were obtained without La2O3 modification. We showed that the source of the stability improvement that the La2O3 in the catalyst not only functioned to restrain the decrease of the support surface area and reduce the sintering of nano-CaCO3, which could limit the decay of the sorption capacity and stability of the catalyst, but also increased the interaction between nickel oxide and the support, which improved the stability of the catalyst by increasing the dispersion of nickel grains and inhibited the growth of nickel grain size. ► The La2O3-modified complex catalyst improved the stability of catalytic activity. ► La2O3 enhanced the interaction of NiO and Al2O3 and inhibited NiAl2O4 formation. ► La2O3 increased the dispersion of NiO grain and inhibited the growth of NiO.