The Old Red Sand is composed of brown-red, red, or orange-yellow semi-cemented and medium-fine sand sediment, mainly distributed along the southeast coast of China. Based on previous studies, this paper summarizes the distribution and forms, sedimentary characteristics, formation mechanism, developing age, reddening process and the paleo-environment, suggesting that the Old Red Sand is mainly aeolian sediment of Late Pleistocene Age. The reddening process is mainly the result of decomposition and oxidation of iron-containing minerals caused by hot and humid tropical and sub-tropical climate. In this study, existing problems are discussed and the prospect of further research is presented as well. Based on the previous studies, this paper summarizes the distribution and forms, sedimentary characteristics, formation mechanism, developing age, reddening process and the paleo-environment, suggesting that the Old Red Sand is mainly aeolian sediment of Late Pleistocene Age. The reddening process is mainly the result of decomposition and oxidation of iron-containing minerals caused by hot and humid tropical and sub-tropical climate. In this study, existing problems are discussed and the prospect of further research is presented as well.