Industrial aluminum nitride(AlN) powder was surface modified with organic carboxylic acid and polyethylene glycol (PEG) as surface modifier and the hydrolysis resistance and modifying mechanism of AlN powder before and after modification were studied.The results showed that the hydrolysis reaction to produce NH3 between AlN and H2O led to the rapid increase of pH value of aqueous solution and generation of much Al(OH)3.The surface coating organic carboxylic acid on AlN particles formed a diffusion barrier between water and AlN surface to improve the hydrolysis resistance of AlN. The pH value of AlN powder after modification slightly increased after soaking in water for 48h

but there was no obvious Al(OH)3 generation.The AlN powder after modification kept higher stability in aqueous ball milling at a high cutting stress.