The lattice-strain engineering of high-entropy-oxide nanoparticles (HEO-NPs) is considered an effective strategy for achieving outstanding performance in various applications. However, lattice-strain engineering independent of the composition variation still confronts significant challenges, with existing modulation techniques difficult to achieve mass production. Herein, a novel continuous-flow synthesis strategy by flame spray pyrolysis (FSP) is proposed, which air varying flow rates is introduced for fast quenching to alter the cooling rate and control the lattice strain of HEO-NPs. Experimental results demonstrate that as the flow rate of air increases from 0 L to 24 L min