SAPO-34 molecular sieves with various special morphologies were successfully synthesized using mixed templates and by varying the silicon content in the gel. The synthesized SAPO-34s were well characterized by XRD, XRF, SEM, N₂ adsorption–desorption, solid state NMR and NH₃–TPD measurements. It is found that a different silicon content not only affects the acidity of the synthesized SAPO-34s, but also changes the morphology dramatically. With the increase of the starting silicon content, the morphology of the synthesized SAPO-34s changes from nanoparticles to regular spherical aggregates. For the methanol to olefin (MTO) reaction, the nanoparticles SAPO-34 S-0.3 with suitable acidity and hierarchical structures exhibit higher selectivity to ethylene plus propylene and longer catalyst lifetime.