The minimized diffusion limitation and completely exposed strong acid sites of the ultrathin zeolites make it an industrially important catalyst especially for converting bulky molecules. However, the structure-controlled and large-scale synthesis of the material is still a challenge. In this work, the direct synthesis of the single-layer MWW zeolite was demonstrated by using hexamethyleneimine and amphiphilic organosilane as structure-directing agents. Characterization results confirmed the formation of the single-layer MWW zeolite with high crystallinity and excellent thermal/hydrothermal stability. The formation mechanism was rigorously revealed as the balanced rates between the nucleation/growth of the MWW nanocrystals and the incorporation of the organosilane into the MWW unit cell, which is further supported by the formation of MWW nanosheets with tunable thickness via simply changing synthesis conditions. The commercially available reagents, well-controlled structure and the high catalytic stability for the alkylation of benzene with 1-dodecene make it an industrially important catalyst.