Abstract: A pharmaceutical composition for treating diseases related to inflammation or injury such as ARDS, comprising: (a) an active material derived from human somatic cells, the active ingredient being an extracellular vesicle produced by human somatic cells; and (b) a pharmaceutically acceptable carrier. The somatic cells are selected from human tissue, bone marrow and/or blood-derived stem cells, etc. The dosage form of the pharmaceutical composition is selected from an atomized inhalation agent, eye drops and nasal drops. The pharmaceutical composition has storage stability and high dispersibility superior to those of a living cell formulation. A method for preparing an extracellular vesicle, comprising steps of culturing human somatic cells, removing cells from a culture system, mixing a culture solution with polyethylene glycol to form an extracellular vesicle modified by PEG, centrifuging, resuspending, etc.