Experimental and computational studies are presented to understand the Ca-alginate sol-gel transition mechanism. Ca-alginate microgel beads are prepared by using electrodispersion process. This method uses electric fields to atomize aqueous mixtures of alginate and CaCO3 nanoparticles from a nozzle into an organic continuous phase containing a soluble organic acid. A critical concentration of alginate is observed for sol-gel transition as a function of the concentration of alginate and CaCO3 nanoparticles. The polymerization kinetic model assumes an initial population of mondispersed alginate precursors, a spatially uniform distributed reactants in the system, an irreversible gelation process and no cyclization to simplify the problem. The model captures the effect of the reactant concentration, the rate constant ratio of the first step reaction (K1, free Ca2+ reaction rate) to the second step reaction (K2, cluster-cluster junction formation rate), and the functionality f on the sol-gel transition boundary. At high calcium ion concentrations, the formation of small alginate clusters is due to the saturation of Ca2+ along the polymer subchains. Typically, a large alginate concentration, large f and small K1/K2 result in fast gel formation. It is concluded that the model results are in reasonable agreement with experimental data and is capable of predicting the sol-gel transition mechanism of the Ca-alginate system.