In recent years the study of bio-deterioration of wall paintings has caught attention of numerous relics conservators. In addition, there has been great progress in methods for protecting such paintings. This paper first describes biological factors causing bio-deterioration, then reviews recent achievements in research on the preservation of wall painting bio-deterioration. Five factors – small animals, insects, plants, microbes and human visitors – are considered, and their effects on the wall paintings are discussed. Protection methods and future research are also discussed. The key to prevent damage by small animals is keeping them out by physical methods; for insects, elimination of the plants that insects rely on is important, as is controlling the insects that feed on other insects; for microorganisms, certain inorganic materials that can prevent the growth of microorganisms can replace currently used biocides; for plants, how to get rid of harmful plants and make use of beneficial plants is the focus of future research; for visitors, the use of replicas or digital imaging is an effective measure. This research will provide important guidance for scientific conservation of wall paintings.