The invention relates to a pretreatment for avoiding the inactivity of assist catalyst in the 2-phenol dimethylmethane compose reaction. Wherein, it comprises first feeding 2-phenol dimethylmethane into pretreater with H-type anode exchange resin, to remove the material that inactivates the catalyst; then feeding the reacted mixture into the assist catalyst reactor to compose. The invention uses H-type anode exchange resin as pretreater to remove the foreign materials as methanol or metal ion to reduce the inactivate speed of assist catalyst and improve the activity of catalyst to reduce the cost. Therefore, it can avoid stopping compose reaction for long time, to reduce cost and improve the yield.