Microorganisms are a major concern in preservation and exhibition of ancient mural paintings. Their identification is a major step leading toward better conservation. Compared with traditional methods, molecular biology - based techniques directly analyze the genetic materials of the microorganisms, avoiding the culturing process and providing a fast and comprehensive method for the identification of major pathogens. Molecular biological techniques were used to detect microorganisms in two tombs built in the 5th century in North China. Pseudonocardia species as the main pathogens was identified. Results provided important information for planning the treatment and prevention of mural damage caused by microorganisms.