PLGA blend and gradient films were designed and prepared to improve the late degradation properties of PLGA films. The gradient films were composed of gradual components of PLGA50/50 and PLGA 75/25, and PLGA 50/50, featuring gradual descents from outside parts to inside parts of the films. Degradation processes of biodegradable PLGA blend and gradient films were also predicted by Monte Carlo simulation to understand the mechanism of degradation. The simulation results indicated that the gradient structure prolonged the mass transfer time of the degradable films, and it induced smoother weight loss than single-component or blend films. The degradation behaviors of single-component, blend and gradient films were experimentally investigated to prove the validity of the models by immersing them into PBS. The experiment indicated that the gradient films have the most stable weight loss curves, which were in well accordance with the simulation by Monte Carlo method.