The accumulation rates of green-oil on the titania-supported palladium catalyst for acetylene removal from ethylene-rich feed were measured through gravimetric analysis, and the changes in activity and selectivity were investigated before and after regeneration. Green-oil accumulation rates decreased with increasing reaction tempera-ture, acetylene concentration and hydrogen to acetylene ratio, while the addition of small amounts CO enhanced the accumulation rate greatly. Volatile and non-volatile fraction of green-oil decomposed at 50-80℃ and 300-400℃, re-spectively, and after regeneration by air the deactivated calalysts restored most activity and selectivity of the fresh ones irrespective of regeneration temperature.