Silicalite nanocrystals were synthesized in a pressurized capillary microreactor at 150 degrees C within 11 min with synthesis solutions aged at 80 or 100 degrees C for 1-6 h. The effects of aging of the synthesis solution and the reaction pressure were examined. The resulting products were characterized by XRD, DLS, TEM, FT-IR and TG-DSC. Aging of the synthesis solution played an important role in shortening the crystallization time of the silicalites. The synthesis pressure should be higher than the saturation vapor pressure of water at 150 degrees C (similar to 0.5 MPa) and silicalite nanocrystals with crystallinities of 70 % and 100 % could be produced from the synthesis solution aged at 100 degrees C for 2 h with residence times of 11 min at 0.7 MPa and I MPa, respectively. The mean particle sizes of these two samples were 102.2 nm and 166.4 nm, respectively. Thus, the crystallization time of the silicalite nanocrystals is shown to be significantly reduced in the capillary microreactor compared to a traditional batch system.