Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible and typical chronic fibrotic lung disease. In recent years, significant progress has been made in the pathophysiology, clinical diagnosis and treatment of IPF. However, to date, there is still no cure for IPF. The second messenger cyclic adenosine monophosphate (cAMP) inhibits fibroblast proliferation or differentiation into myofibroblasts during the development of IPF. Phosphodiesterase 4 (PDE4) is a major camp-degrading enzyme in lung fibroblasts, which is up-regulated during the progression of fibrosis. PDE4 inhibitors have anti-fibrosis effects in vivo and in vitro in IPF models. In addition, PDE4 is widely involved in inflammatory processes, which are also active in the pathogenesis of IPF. Thus, PDE4 inhibition is a potential therapeutic approach for IPF. This article reviews the pathogenesis of IPF and the physiological function of PDE subtype 4 inhibitors in the treatment of IPF.