La-modified NaY zeolites have been prepared through impregnation and in situ synthesis methods. The surface structure of the obtained zeolites was then characterised by XRD, UV-Vis DRS, FT-Far-IR, Raman spectra, H-2-TPR, N-2 adsorption, and NH3-TPD. The results of the catalytic dehydration reaction of lactic acid showed that the La/NaY catalyst prepared by impregnation method exhibited higher selectivity to acrylic acid than the La-NaY prepared by the in situ synthesis. The characterisation results indicated that the enhanced catalytic performance could be attributed to the difference of La3+ ion location caused by the different preparation protocols, which would influence the electric field distribution of zeolites cages, the reactant adsorption, chemical activation, and the reaction path.