Analytical solutions of transient concentration of degraded components inside cylindrical and slab-type PLGA particles immersed in infinite medium were derived by solving reaction-diffusion equations of autocatalytic reaction using eigenfunction expansion method. The resulting average concentrations were compared with the modeling results of spherical PLGA particles by Versypt and her colleagues to study the effect of particle morphology on the autocatalytic reaction. Mass transfer resistance inside and outside of the particles was also considered using Biot number, and its effects on the concentration inside particles with various morphologies were also studied by solving reaction-diffusion equation. To predict transient concentration in surrounding medium, coupled differential equations were solved for the three shapes of PLGA particles by assuming finite volume of the decomposition system. Mathematical solutions were obtained by Laplace transform, and the results were compared for the PLGA particles with different shapes depending on Thiele modulus and particle volume fraction.