Nano-structured magnesium hydroxide (nano-MH) has been added into LDPE/LLDPE, the technological parameters, flame and mechanical properties, M.F.R. of LDPE/LLDPE/nano-MH samples have been examined. It is indicated two time extruder pelletization is a good technological route, which can make nano-MH disperse evenly in PE. The optimum rotational speed of screws changes from 37 to 42 rad/min, the die pressure changes from 35 to 61.5 bar. Nano-MH has good flame retardant and smoke suppressing properties. The samples added 60% nano-MH can reach UL94 FV-0 flame retardant rating. When nano-MH content is more than 40%, no smoke emits. With nano-MH content increases, the tensile strength, impact strength, elongation and M.F.R decreases, Young’s modulus increases.