add 100 kg of phenylethyl phenol into the reaction kettle, slowly raise the temperature to 50 ℃, then add 8 kg of 50% NaOH, then continue to raise the temperature to 120 ℃, and dehydrate under reduced pressure. After the water is basically removed, the temperature is raised to 140 ℃, dehydrated under reduced pressure for 10 min, then the air in the kettle is replaced with nitrogen, 230 kg of ethylene oxide is added in batches, and the reaction is carried out at 150~160 ℃ and 0.15 MPa for 2 h. Sampling to measure the cloud point. When the cloud point is 74.5~75.5 ℃, cool to 80 ℃, and adjust the pH value to 5.0~6.0 with glacial acetic acid.