Background　Relaxin（RLX） was initially considered to be a pregnancy-related hormone. Recent research indicates that RLX has a protective effect on the lung， the protections lie in anti-fibrosis， reduction of airway remodeling， dilation of blood vessels， amelioration of lung ischemia/reperfusion （I/R） injury.　Objective　Review progresses of studies on the treatment and mechanism of RLX on lung diseases to provide ideas for future study of RLX on lungs.　Content　Briefly introduce the molecular structure of RLX family， receptors and signal transduction pathways， mainly summarize the treatment and its mechanism of RLX for different types of lung diseases.　Trends　Many studies have confirmed the therapeutic effect of RLX on lung diseases， but there is still a certain distance away from clinical application.