The SAPO-11 zeolite is widely used in the hydroisomerization of n-paraffins due to its unique shape selectivity, and the particle size plays an important role in the catalytic performance. Herein, multi-scale SAPO-11 zeolites with different particle sizes (65 nm to 4.5 μm) are successfully synthesized via a modified dry-gel conversion method by controlling the nucleation rate and the growth rate of the crystal. The resulting samples were characterized by XRD, SEM, N2 adsorption desorption, NH3-TPD, Py-IR and 29Si MAS NMR. These solid results indicate that the change in particle size of SAPO-11 has a large effect on its structure and acidity. Furthermore, the n-dodecane hydroisomerization reaction was investigated in this work, and the experimental results show that the prepared bifunctional Pt/SAPO-11-10% catalyst has the highest iso-dodecane yield (70.9%) with a conversion of 93.5% among all the samples, which could be ascribed to the synergistic effect between the suitable particle size and acid sites, which enhanced its catalytic performance.