This review summarized the molecular mechanism and pathological changes in different cell subsets in the IPF lung, highlighting that aging, apoptosis resistance, autophagy defects, organelle dysfunction, metabolic abnormalities, and epigenetic changes are the main inducing factors of IPF, whereas the TGF-β/Smads pathway, Fas/FasL apoptotic pathway, and PI3K/Akt signal transduction pathway also play important roles in the development of IPF. This evidence concerns the gene FAS and idiopathic pulmonary fibrosis.