put 1 mol phenol into the reaction kettle, heat and melt, cool to 50 ℃, and add sulfuric acid dropwise as catalyst. Raise the temperature to 120 ℃, start dropping m mol styrene, alkylate melon under 130~150 restraint, cool the temperature after dropping styrene, drive the feed liquid into a condensation kettle, add 1 mol formaldehyde under stirring to carry out condensation reaction, the reaction is catalyzed by sodium hydroxide, the temperature is controlled at 80~85 ℃, the temperature is cooled to 40 ℃ after 1 h of reaction, and the water is removed by vacuum. Then nitrogen is used to drive the air in the kettle, then n mol of ethylene oxide is passed, ethylene oxide is passed to the proportional quantity, then the cloud point of 1% aqueous solution is sampled and measured, and the reaction is completed at about 80 ℃. The feed liquid is driven into the neutralization kettle, and the pH value is adjusted to 5.0~7.0 with acetic acid. The finished product is packaged by cooling and discharging.