A continuous, microfluidic-based, seed-mediated synthesis of high-purity gold nanoplates with different thicknesses was developed. The thickness of the nanoplates can be fairly tuned from less than 1 nm to a few nm by varying the flow rate. Depending on the thickness, the obtained nanoplates could be rigid and flat-surfaced with thicknesses larger than 2 nm or flexible with crumpled or rolled shapes when the thickness is around 1 nm. These nanoplates are poly-crystalline with different crystal faces and show high electrochemical activity towards glucose oxidation.