A　series　of　polycarboxylate　superplasticizer　(PCE)　polymers　were　synthesized　from　acrylic　acid　(AA)　and　isoprenyloxy　polyethylene　glycol　ether　(IPEG)　at　the　mole　ratios　of　3.0,　4.2,　5.0　and　6.0.　In　this　study,　the　molecular　weight　properties　of　PCE　polymers　were　recorded　by　size　exclusion　chromatography　with　the　time　interval　of　1　h.　Mini　slump　test　was　used　to　detect　the　dispersing　effectiveness　of　PCE　polymer　in　cement　paste.　The　results　indicated　that　the　reaction　rate　of　monomers,　conversion　of　52IPEG　macromonomer　and　molecular　weight　of　PCE　polymers　increased　with　the　general　adding　ratio　of　AA　to　IPEG　macromonomers　while　the　side　chain　density　of　PCE　polymers　decreased.　PCE　polymers　possessed　molecular　weight　around　30,000　g/mol　with　low　side　chain　density,　and　long　main　chain　length　presented　high　initial　dispersing　effectiveness　at　the　low　dosage　around　0.12%.　The　majority　of　effective　PCE　polymers　were　formed　during　the　adding　period　of　acrylic　acid　in　the　first　3　h.