A halogen-free flame retardant capable of well keeping performance of polypropylene. A method for preparing the halogen-free flame retardant comprises: 1, heating 1,3,5-tris(2-hydroxyethyl)cyanuric acid; 2, enabling 1,3,5-tris(2-hydroxyethyl)cyanuric acid to undergo a polymerization reaction under the action of a catalyst, so as to obtain a 1,3,5-tris(2-hydroxyethyl)cyanuric acid polymer; 3, preparing a 1,3,5-tris(2-hydroxyethyl)cyanuric acid polymer charring agent; and 4, mixing ammonium polyphosphate, a triazine charring agent and the 1,3,5-tris(2-hydroxyethyl)cyanuric acid polymer charring agent to carry out surface treatment, so as to finally obtain the halogen-free flame retardant. In addition, also provided is the halogen-free flame retardant prepared by using the method, for use in the preparation of flame-retardant polypropylene. Properties of the prepared flame-retardant polypropylene are superior to those of traditional flame-retardant polypropylene of an ammonium polyphosphate-triazine charring agent system. The obtained halogen-free flame retardant has better compatibility with polypropylene resin, can be comparable with a bromine-antimony flame-retardant system, is superior to bromine-antimony in terms of flame retardance of glowing filaments, and is environmentally-friendlier and very competitive in cost.
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