A novel intumnescent flame melamine salt of dipentaerythriol phosphate (MDP), was prepared from dipentaerythritol (DPE) polyphosphoric acid, and melamine. The flammability, combustion behavior, and thermal degradation and stability of PP-MDP were characterized. When MDP loading was 20 wt%, LOI values of the composites reached up to 27%, and UL94 rating, V-2. PP-MDP containing 1 wt% Cu-ZSM-5 presented the highest LOI value of 30.5% and UL94 rating, V-0, and released lest heat during cone test. TG data showed that the thermal degradation of PP was improved by the addition of MDP. While the loading of ZSM-5 was 1 wt% or higher, the main weight loss delayed with 50oC, and 80oC, compared with PP and PP-MDP respectively. The appropriate loading Cu-ZSM-5 made PP-MDP possess higher thermal oxidative stability. By SEM, the formation of a dense and thick char layer was observed on the char layer of PP-MDP-containing Cu-ZSM-5, responsible for high flame retardancy. So, the synergistic flame retardancy effects of MDP and Cu-ZSM-5 on PP existed. The mechanism of synergistic effect of Cu-ZSM-5 zeolite on flame retarded PP by MDP was discussed.