The objective of the paper is to characterize venlafaxine's release behavior in vitro following the preparation of venlafaxine hydrochloride sustained-release pellets.At first, the drug substance was microencapsulated into an EC solution to prepare fast-release pellets by a centrifugal granulator; then, the fast-release pellets was used as the core and microencapsulated into aqueous dispersed costing materials made of Eudragit NE 30D to prepare sustained-release pellets; next, the fast-release pellets and sustained-release pellets were mixed with a ratio of 1:2 to make the final sustained-release pellets.The effects of coating thicknesses on the sustained-release parameters were analyzed.The results showed that the optimal sustained release behavior in vitro of the sustained release pellets mixed from fast-release pellets and sustained-release pellets with a ratio of 1:2 was selected when the amount of coating materials was 20% of total weightIt was concluded that the venlafaxine hydrochloride sustained-release pellets provided a rather good sustained-release efficiency.