Single- and poly-crystalline silicalite/HZSM-5 core-shell composite catalysts were synthesized by optimizing the silicalite coating conditions. At low molar ratios of SiO2 (fumed silica) and TPAOH in the coating solutions, a crystal growth of silicalite layer on the HZSM-5 surface was dominant instead of a homogeneous nucleation in the solution. The mass gain after the coating was also inhibited at low molar ratios of silica source and TPAOH. High para-selectivities of silicalite/HZSM-5 composites in the toluene alkylation with methanol were obtained over the single crystal-like silicalite/H-ZSM-5 composite catalyst prepared by one coating process.