Recently, the selective hydrogenation of C=C bond in isophorone (IP) has been a hot issue. Egg-shelled catalysts Pd/Al2O3 were prepared by incipient impregnation method, and effects of supports calcination temperature, egg-shell depth, Pd loading and particle size, type of solvents and reaction conditions on selective hydrogenation of isophorone (IP) were well investigated using fixed-bed hydrogenation microreactor. Results indicate that egg-shelled Pd/Al2O3 is a perfect catalyst for the selective hydrogenation of IP to prepare 3,3,5 - trimethylcyclohexanone (TMCH), and the conversion of IP and selectivity of TMCH both reach up to 99.5% at mild conditions, showing good prospects for industrial application.