In this study, a hexagonal EMT zeolite (denoted as SEMC-2) was successfully fabricated by combination of template 18-crown-6 ether with a steam crystallization (SAC) method. The effects of both SAC time and temperature on the crystal form were emphatically studied at the Na2O/Al2O3 molar ratio of 2.4. The regular hexagonal platelet SEMC-2 zeolite with diameter of 3～4 μm and thickness of 300～400 nm was synthesized under crystallization temperature 110℃, crystallization time 6 days. Similar to EMT zeolite prepared by the traditional hydrothermal crystallization method (denoted as HEMC-2), SEMC-2 zeolite could also deeply purify the trace amounts of polar methanol and propanal to below mole percent 0.0001% from gaseous olefins at an initial mole percent 0.02% or 0.1%. Moreover, the breakthrough times and cumulative adsorption amounts of HEMC-2 and SEMC-2 zeolite had no obvious difference. The regeneration experiment indicated that the SEMC-2 zeolite had more stable structure and longer service life. The in-situ FTIR spectra demonstrated the adsorption processes of the SEMC-2 zeolite for methanol and propanal were a physical adsorption mainly via interaction between the polar-oxygenated compounds O lone-pair eletrons and the SEMC-2 zeolite Na+.