A cyclical epitaxial deposition system and a gas distribution module are provided. The gas distribution module includes an inflow element having a plurality of inlet holes, a guide assembly, and an outflow element. The guide assembly disposed between the inflow and outflow elements includes a plurality of guide channels separate from one another and a plurality of temporary gas retention trenches respectively corresponding to the guide channels. Each of the guide channels is in fluid communication with the corresponding inlet hole. The outflow element has a plurality of diffusion regions respectively corresponding to the gas retention trenches, and a plurality of outlet channels respectively corresponding to the diffusion regions. Each of the diffusion regions has a plurality of diffusion apertures, and each of the temporary gas retention trenches is in fluid communication with the corresponding outlet channel through the diffusion apertures in the corresponding diffusion region.