This paper details an experimental investigation involving shaking table tests on two composite foundations consisting of geosynthetic encased stone columns (GESC) with varying levels of geosynthetic encasement stiffness. The main objective is to examine the effect of the stiffness of geosynthetic encasement on the deformation behavior of the foundation models subjected to dynamic loading. The scaled-down foundation models were scaled in accordance with the similitude principles considering model size, stiffness of geosynthetic encasement, and input motions. The construction of the foundation models involved the use of gravel, sand, and geotextile reinforcement, and subsequently subjected to a sequence of sinusoidal excitations with rising amplitude. Results indicate the cumulative column settlements and soil settlements of the two foundation models increase notably as the input acceleration rises. The model with high stiffness of geosynthetic encasement has smaller settlements under the identical input motions in comparison to the model with low stiffness of geosynthetic encasement and has better seismic behavior in terms of settlement. In summary, with an increase in the stiffness of geosynthetic encasement, the deformation behavior of GESC composite foundation under dynamic loading is effectively improved.