The invention discloses a method for preparing a modified hydroxyl ester 
polymer emulsion. Required raw materials comprise the following components in parts by 
mass: 1.0-4.2 parts of a hydrophilic small 
monomer for emulsification, 1.7-4.5 parts of a hydrophobic small 
monomer for emulsification, 18-51 parts of a hydroxyl small 
monomer, 0.05-0.26 part of an 
emulsion initiator, 2.2-5.4 parts of an initiator a, 3.5-6.6 parts of an initiator b, 380-450 parts of an ester small monomer, 6.2-9.3 parts of a crosslinking agent, 0.06-0.28 part of a 
chain transfer agent, 0.5-1.0 part of 
graphene oxide, 15-40 parts of polyether, 5-10 parts of a neutralizer, 5-10 parts of a pH 
regulator, 2.0-6.5 parts of an emulsifier 
promoter, 0.4-1.3 parts of a liquid film 
enhancer and the balance of water, wherein the total parts by 
mass are 1000, and the 
solid content is 50%. The waterproof 
coating disclosed by the invention is suitable for 
cement mixing; due to a large number of hydroxyl groups, 
calcium ions can be stably complexed, 
calcium ion hydrolysis can be effectively inhibited, the 
cement strength can be increased, and the waterproof effect can be improved; due to 
hydrogen bonds in molecules of the hydroxyl groups, the internal 
binding force of the 
polymer can be improved, and the adhesion of the 
polymer with a matrix can be improved through a good hydrophilic effect; due to addition of the 
graphene oxide, the tensile strength of a 
polymer emulsion in film formation can be remarkably improved; and the 
water resistance can be also improved to a certain extent.