With Methyl acetoacetate (MAA) and Neopentyl glycol diacrylate (NPGDA) as raw materials, a linear polymer, Poly (Methyl acetoacetate?Neopentyl glycol diacrylate) (P(MAA?NPGDA)),was prepared via a base?catalyzed Michael addition reaction to extend the molecular chain. The synthesized samples were characterized and analyzed by Fourier transform infrared spectroscopy (FTIR),proton nuclear magnetic resonance spectroscopy （¹H NMR）,differential scanning calorimetry（DSC）,high?performance liquid chromatography （HPLC） and gel permeation chromatography（GPC）. The effects of different catalysts on the relative molecular weight growth, heat release rate, and double bond conversion rate of monomers during the reaction were investigated at various temperatures. Furthermore, by using 1,8?Diazabicyclo[5.4.0]undec?7?ene (DBU) as the catalyst, the impacts of varying reaction temperatures, catalyst concentrations, and the ratio of n(MAA) to n(NPGDA) on the molecular weight growth of linear polymers were examined. Under the tested conditions, in a reaction temperature range of 30-40 ℃ with a DBU mass fraction of 2%, and a MAA?to?NPGDA monomer ratio of 1.00∶1.00, the growth rate of P(MAA?NPGDA) molecular weight was relatively stable, and the polymer ultimately reaches a relatively high relative molecular weight.