External gelation process of Ca-alginate gel with a controlled supply of CaCl2 to alginate solution was experimentally and numerically investigated. A single Na-alginate solution film was prepared and suspended in a closed chamber of CaCl2 spray droplets. The collected mass of CaCl2 by the film increases as the spraying time increases. The collection efficiency (E) between the film and CaCl2 droplets was averagely 0.0015. The degree of gelation (P) of the film was found to be alginate and CaCl2 solution concentration dependent. The experimental results of the mass of CaCl2 droplets collected by the film and the E were in good agreement with the numerical results. The concentration-distance profiles of Ca2+ cation, alginate, and Ca-alginate gel in the film were determined using the one-dimensional diffusion-reaction model. The model is useful to determine the P of the Ca-alginate gel film produced using a limited supply of CaCl2. (C) 2018 Published by Elsevier Ltd.