The invention discloses an application of hesperidin in preparation of a medicament for preventing and / or treating pulmonary fibrosis diseases. By virtue of experimental verification, the hesperidin can achieve an effect of preventing and treating pulmonary fibrosis by inhibiting lung fibroblast proliferation, inhibiting epithelium-mesenchyme conversion of alveolar epithelial cells and inhibiting lung fibroblast activation, so that the hesperidin can achieve a new application in preparation of the medicament for preventing and / or treating the pulmonary fibrosis diseases. The application relates to various medicament dosage forms such as capsules, drop pills, aerosol preparations, spraying agents, tablets, granules and injections prepared from the hesperidin. Moreover, the application also relates to a composition, which is formed by taking the hesperidin as a main component, for preventing and treating the pulmonary fibrosis.