Solid-phase PAMAM dendrimer was synthesized by the repetitive addition of a branching unit to silica gel. All synthesis steps were monitored by infrared spectroscopy to investigate the reaction rate. Based on the measurements of infrared spectra, which showed the ester group varied as a function of reaction time, a reaction kinetics model was proposed and simulated. FT-IR and TGA measurements suggested that a ‘cross-linking’ reaction occurred in amidation process and generated structural defects, which decreased the grafted amount of dendrimer on silica gel. In addition, the analysis of reaction rate constants indicated that due to the formation of an intermediate, Michael addition of methyl acrylate to diamine was probably hindered by steric crowding.