The effects of chain extenders and cross linkers on the mechanical characteristics of the binder film of the NEPE propellant at 50 ℃ were experimentally studied. The results indicate that the aliphatic and low molecular polyether diols (chain extenders) improves the mechanical characteristics of the binder films at high temperature, and the three types of triols (cross linkers) increases the maximum stress of the binder film and decreases the maximum elongation of the bind film. It is found that the aliphatic diols might cause the exudation of nitrate esters from the binder film during the curing process.