The reaction kinetic parameters have an important guiding significance for the prepolymerization of acrolein-pentaerythritol resin. Online IR method was used to study the prepolymerization reaction kinetics of acrolein-pentaerythritol resin. When the reaction temperature was 338.15, 348.15 K and 358.15 K, and the dosage of diethyl sulfate (DES) as catalyst was 2% and 4% respectively, by monitoring the change in concentration of functional group =CH₂ in the reaction system, the kinetic equation of the polymerization reaction was obtained by calculation and the mechanical property of cured product was studied. The results show that the reaction is a second-order reaction, but the apprent reaction rate and reaction activation energy in the early stage and late stage for the reaction have a large difference. When the dosage of DES is 2%, the apparent activation energy in the early stage and late stage of the reaction is 36.5 kJ·mol^-1 and 49.6 kJ·mol^-1 respectively. When the dosage of DES is 4%, the apparent activation energy in the early stage and late stage of the reaction is 61.0 kJ·mol^-1 and 69.1 kJ·mol^-1 respectively. When the dosage of DES is 2% and 4%, the effect of dosage of DES on the mechanical property of cured product is not obvious. The reaction temperature on the mechanical property of cured product has a remarkable influence, when the dosage of DES is 2% and 4%, the maximum tensile strength appeared at 338.15 K is 41.99 MPa and 41.17 MPa, respectively, the maximum elongation at break appeared at 358.15 K is 8.47% and 7.27%, respectively.