One of the most important applications of metal hydrides is for heat pumps. A two-stage heat pump is superior to a single-stage heat pump because the for mer has higher efficiency and wider operational temperature range. This paper carries out a systematic study on two-stage hear pumps. Six cycles of two-stage heat primps are analysed and compared, the selection of metal hydrides for these heat pumps is discussed the actual COP equations are derived and the effects of some parameters on COP are examined. The study shows that the low-pressure-side two-stage heat pump is suitable for heat upgrading and the high-pressure-side two-stage heat pumps for heat amplifying and refrigerating. For high efficiency of the systems, the metal hydrides used should have Delta H-H/Delta H-M less than or equal to 1 and Delta H-M/Delta H-L less than or equal to 1 for a heat-upgrading heat pump and have Delta H-H/Delta H-M greater than or equal to 1 and Delta H-M/Delta H-L less than or equal to 1 for heat-amplifying and refrigerating heat pumps. In order to obtain a high COP, it is important to develop metal hydrides with wider and flatter plateaux in their P-C-T curves, to reduce the total sensible heat capacity of the reactors and metal hydrides, and to recover some part of the sensible hear between reactors.