［Objective］ To enhance both the flame retardancy and mechanical properties of polyurea elastomer（PUA） composites，addressing the issue of mechanical performance degradationcaused by traditional flame-retardant modifications.［Methods］ Halloysite nanotubes（HNT） were internally modified with amino trimethylene phosphonic acid（ATMP） as a flame retardant. The modified ATMP-HNT was then incorporated into polyurea to prepare PUA/ATMP-HNT composites.The flame retardancy，combustion behavior，and mechanical properties of pure PUA，PUA/HNT（with 5% unmodified HNT）and PUA/ATMP-HNT（with 5% ATMP-HNT）were comparatively investigated using cone calorimetry，vertical burning tests，and tensile testing.［Results］During the 600 s cone calorimeter test，compared to pure PUA，the PUA/ATMP-HNT composite exhibited a 7. 2% reduction in total heat release，a 19. 9% increase in limiting oxygen index（LOI）， a 26. 2% decrease in total smoke production，and a 10. 1% improvement in tensile strength.［Conclusion］ ATMP-modified halloysite nanotubes significantly improve both the flame retardancy and mechanical performance of polyurea composites. This approach effectively reduces fire hazards while preserving the structuralintegrity of the material，demonstrating promising potential for practical applications.