The influence of different content of magnesium hydroxide(MDH) on the flame-retardancy of ethylene-vinyl acetate(EVM) /nitrile rubber(NBR) was studied by the limiting oxygen index(LOI) and the cone calorimeter in this paper.The results indicate that the flame-retardancy of EVM/NBR vulcanizates is improved due to the addition of flame retardant.The more content of flame retardant MDH,the higher LOI is,the better the flame-retardancy is.The results of the cone calorimeter measurement show that the heat release rate(HRR) and mass loss rate apparently decrease as the increase of MDH content.And it is found that there are two peaks in the HRR-t curve and the time where the peak occurs becomes lengthened.The content of flame retardant MDH reaches 180 phr to gain the best flame retardancy.