The flame retardancy of polypropylene is improved through the blending of the proper ratio of halogens and phosphorus compound with the polymer. The flame retardancy of modified polypropylene was measured with use of TGA and oxygen index tester. The decomposition temperature of the pure polypropylene is 370℃. On the other hand, that of the blended polypropylene is in the range of 391℃-446℃. The oxygen index of pure polypropylene is 16 and that of the blended polypropylene is above 26. From these results, it was demonstrated that the flame retardants in blended polypropylene show good flame retardancy without severe damage of mechanical properties.