Abstract: Effects of treatment conditions such as pH, enzyme dosage, time and temperature were investigated on the removal of lipophilic extractives from wheat straw (WS) using Candida cylindracea lipases. The influences of lipase treatment on WS weight gain percent from acetylation and the inner bonding strength of WS particle board were also examined. The WS lipophilic extractives were analyzed by GCMS. Test results showed that the removal rate of lipophilic extractives was 62 % under the optimal conditions: 50 ℃, pH 7.5, lipase dosage 7.5×10-3 mol/(min·g)(based on ovendried WS), time 8 h. The inner bonding strength of particle board manufactured from the treated WS could increase by 4.5 fold due to the increase in —OH concentration on the WS surface. The GCMS results showed the main components of nhexane extractives of WS were fatty acids, waxes and steroids, and their removal rates by lipases were 79.67 %, 69.04 % and 41.47 %, respectively. There were some glycerides, fatty alcohols , silicon oxide and phenolics in the extractives, and their removal rates by lipases were 80.98 %, 63.30 %, 43.31 % and 36.35 %, respectively. It was concluded that the removal of the lipophilic extractives from the WS by lipases could increase the hydroxyl group concentration and the mechanic performance of WS particle board.