Thrombopoietin (TPO) is also referred to as the c-mpl ligand or megakaryocyte growth and development factor, inducing thrombopoiesis by proliferation of megakaryocyte progenitors and promoting endoreplicatton of mature megakaryocytes, t The identification of TPO, and the demonstration that administration to normal experimental animals with recombinant TPO results in a marked increase in platelets count, 2 has opened the possibility of using TPO to rescue patients from life-threatening thrombocytopenia with high dose chemotherapy and radiotherapy. But recombinant TPO is a foreign protein and has adverse effects on patients to different extent. This study is to establish a new TPO administration by gene therapeutic methods, i.e. that after transferred into animals, the TPO gene expresses functional TPO in vivo and maintains high platelet level.