The invention discloses a polycarboxylic acid building admixture containing a phenyl structure. A molecular structural formula I of the admixture is shown in the description; in the formula I, the sum of a and b is greater than 0 and smaller than or equal to 200, the sum of c and d is greater than 0 and smaller than or equal to 200 and e is greater than 0 and smaller than or equal to 100; n is greater than 0 and smaller than or equal to 300; m is 1, 2 or 3; R1 is straight-chain polyethylene glycol; a molecular structural formula II of the R1 is shown in the description; in the formula II, n is greater than 10 and smaller than 90; the R2 is straight-chain polyethylene glycol monomethyl ether; a molecular structural formula III of the R2 is shown in the description; in the formula III, n is greater than 10 and smaller than 90; the R3 is at least one of -H or -Na; R4 is at least one of -H or -CH3. According to the polycarboxylic acid building admixture disclosed by the invention, a maleic anhydride esterification product containing the phenyl and unsaturated carboxylic acid undergo polymerization reaction to synthesize a low molecular weight polymer; the technical problem of low reaction activity of a maleic anhydride structure is overcome; the polycarboxylic acid building admixture containing the phenyl structure is synthesized; compared with the prior art, the building admixture has the advantages of higher initial water reducing rate and delayed coagulation and slump retaining properties.