The invention discloses application of the n-butyl alcohol part of ethanol extract of herba violae as a drug for preventing immunological liver injury, which belongs to the technical field of traditional Chinese medicine application. An experiment proves that the n-butyl alcohol part of the ethanol extract of herba violae has a broad application prospect as a drug for reducing liver injury causedby TNF-aAlpha or IFN-gGamma. The invention provides a novel application for the n-butyl alcohol part of the ethanol extract of herba violae, and also provides a new medicinal source for the preventionof immunological liver injury. By studying the protective effect of the n-butyl alcohol part of the ethanol extract of herba violae on immunological liver injury, a basis for the application of the n-butyl alcohol part of the ethanol extract of herba violae in preventing immunological liver injury is obtained, the medicinal resource of herba violae is further reasonably utilized, and data supportis provided for the development of herba violae as a drug.