This study was aimed to investigate the efficacy of haploidentical hematopoietic stem cell transplantation (hi-HSCT) combined with umbilical cord mesenchymal stem cells (MSC) using modified conditioning regimen for the treatment of patients with refractory and relapsed or high risk malignant hematologic diseases, the clinical efficacy in 30 patients with refractory and relapsed or high risk malignant, who voluntarily received HSCT was analyzed. Among the 30 patients there were 4 relapsed cases and 26 cases of high risk malignant hematologic diseases. The above-mentioned patients included 15 AML, 9 ALL, 3 pro T lymphoblast lymphoma/leukemia, 1 spleen boundary zone lymphoma IVB, 1 NK/T lymphoma and 1 Burkitt lymphoma IVB. The results showed that the implantation was achieved in all 30 cases, among them 19 cases (63%) had aGVHD and 6 cases (20%) had III-IV aGVHD, 8 cases (32%) had cGVHD including 1 case of extensive and 7 cases of limited. Three cases relapsed at 300 days (128-455 d) after transplantation. 8 cases died, among them 1 case died of relapse, 2 cases died of IV aGVHD with relapse, 5 cases died of infection and organ failure. It is concluded, the efficacy of hi-HSCT combined with umbilical cord MSC for treatment of patients with refractory and relapsed or high risk malignant hematologic diseases is favorable.