Yttrium oxide hydroxide nitrate nanorods were prepared via a facile hydrothermal method using PEG-6000 as template in Y(NO3)3 and KOH reactant system. The effect of hydrothermal treatment time on the crystallite structure, the crystallite shape and size was investigated by XRD and FE-SEM measurements. XRD results showed that the main phase of the as-prepared product was Y4O(OH)9NO3 crystal of monoclinic phase. FE-SEM images displayed that the size of the nanorods grows large with increasing time from 5h to 24h. Furthermore, no shape change was found, demonstrating that the as grown nanorods are stable when the reaction time increased from 1h to 24 h. Dissolution recrystallization process was proposed to explain the growth process of Y4O(OH)9NO3 nanorods.