Thermal decomposition properties and hazards of nitrate explosives containing Mg(BHx)(y) were investigated by thermogravimetry-differential scanning calorimetry (TG-DSC), accelerating rate calorimeter (ARC) and characteristic drop height impact sensitivity tests. Results show that the addition of Mg(BHx)(y) to nitrate explosives led to increase in the volatilization temperature of nitroglycerine in the nitrate explosive. It was not the thermolysis product of Mg(BHx)(y), but Mg(BHx)(y) itself acted on the nitrate explosive in the TG-DSC tests. Kinetic parameters and thermal hazard assessment parameters were calculated based on ARC data. Results show that a mixture of the nitrate explosive with Mg(BHx)(y) had higher apparent activation energy and lower thermal hazard. Experiments of characteristic drop height showed that Mg(BHx)(y) reduced the impact sensitivity of nitrate explosives.