In this article, polyethylene glycol-acrylamide (PEG-AAm) hydrogels were experimentally prepared with a matrix structure and their swelling behaviors were tested. Different amounts of polyethylene glycol, acrylic acid, and acrylamide were added, and an optimum case was discovered. Effect of some parameters on the swelling was then investigated. A dynamic model based on the Maxwell-Stefan equation, Nernst-Planck equation, and Donnan theory was developed to consider the swelling behavior of hydrogels. These equations were applied to model the buffer diffusion inside the hydrogels in the swelling process. COMSOL software was also applied to simulate the swelling behavior in the hydrogels. The results showed that the data obtained from the modeling were in good agreement with the experimental data (the deviation value was around 16%). Further, COMSOL was able to simulate water diffusion process in the hydrogels, properly.