100 kg of phenylethyl phenol is added into the reaction kettle, heated to 50 ℃, then 8 kg of 50% NaOH is added, heated to 100 ℃ under stirring, then heated to 120 ℃, vacuum pump is turned on, and dehydrated under reduced pressure. After dehydration, the air in the kettle is changed with nitrogen, and 354 kg of ethylene oxide is slowly added. During the feeding process, the reaction pressure is controlled at 0.05~0.15 MPa. After the feeding is completed, keep the temperature for 1.5 h. When the pressure in the kettle no longer drops, the reaction ends. Sampling to measure the cloud point, the cloud point is within the range of 100 ℃ 1.5 ℃, start to cool down, and adjust the pH value to 5.0~6.0 with glacial acetic acid at 80 ℃.