The invention discloses cis-
butenedioic acid di-2-ethylhexyl ester, a method for synthesizing the same and application of the cis-
butenedioic acid di-2-ethylhexyl ester to preparing polycarboxylic 
acid water reducing agents. The cis-
butenedioic acid di-2-ethylhexyl ester, the method and the application have the advantages that 
maleic acid monoester is generated from 
maleic anhydride by means of alcoholysis, then the 
maleic acid monoester is polymerized with 
ethylene oxide or propylene 
epoxide and is polymerized with 
ethylene oxide to generate novel diester which is the cis-butenedioic acid di-2-ethylhexyl ester, 
acrylate can be substituted with the cis-butenedioic acid di-2-ethylhexyl ester for preparing the polycarboxylic 
acid water reducing agents, accordingly, the 
slump retention performance of the polycarboxylic 
acid water reducing agents can be improved, and low 
slump loss of premixed concrete in two hours can be guaranteed; integral reaction, structures and molecular weights canbe controlled, the reaction can be smoothly and steadily carried out, 
water production can be prevented, the cis-butenedioic acid di-2-ethylhexyl ester is green and 
environmentally friendly and is high in yield, 
preparation procedures are simple, and industrial production can be facilitated. A 
structural formula of the cis-butenedioic acid di-2-ethylhexyl ester is shown. An R in the 
structural formula represents methyl or ethyl or propyl or 
isopropyl or normal-butyl or 
diethylene glycol mono-methyl 
ether, an m and an n in the 
structural formula are integers, the m ranges from 0 to 8, and the nranges from 1 to 15.