Background　The acute lung injury(ALI) is a common critical disease in clinics, which is caused by direct or indirect injuries. The main characteristics are acute pulmonary edema and hyoxemia. ALI is still lack of effective therapy method. The mortality is about 30%-50%. Mesenchymal stem cells(MSC) are pluripotential stem cell, which have the basic ability of proliferation and differentiation. MSC can treat the acute lung injury due to its reparation role of damage, immunoregulation and anti-inflammation.　Objective　Summarizing the characteristics, common sources and usages of MSC. Verifying the mechanism and potential clinical utility of MSC in the therapy of acute lung injury.　Content　Through implantation, homing and immunoregulation, reducing pulmonary edema, antibiotic action, transference of mitochondria and formation of microvesicle and microtubule, MSC play a therapeutic role on ALI.　Trend　Large scale clinical trials are needed to prove that MSC can cure the ALI. The optimum time, mode, and dosage of transplantation have no unified standard yet. Whether there are some drawbacks remains to be test.