The invention provides a flame retardant composite which contains intumescent flame retardant, wherein, the composite also contains compound material which comprises a kernel part and a shell part, the shell part enwraps the kernel part, the kernel part is hydroxide containing a coupling agent, the shell part is resin formed by one or more than one of the monomers containing crylic acid or acrylicester structural unit, or resin formed by one or more than one of the monomers containing crylic acid or acrylicester structural unit and styrene and/or butadiene, and the hydroxide is magnesium hydroxide and/or aluminum hydroxide. The invention also provides a thermoplastic elastomer which is a product obtained by carrying out a reaction of a mixture of EPOR, polypropylene, crosslinker and flameretardant material at smelting temperature, wherein, the flame retardant material is the flame retardant composite provided in the invention. The flame retardant composite and the thermoplastic elastomer provided in the invention have outstanding flame retardant performance.