In　this　paper　a　new　spectral　envelope　estimation　method　based　on　radial　basis　function　(RBF)　neural　network　is　proposed　for　implementing　a　blind　bandwidth　extension　method　of　audio　signals.　To　make　the　sub-band　envelope　of　high-frequency　(HF)　components　accurately　recovered,　the　RBF　neural　network　is　utilized　to　fit　the　relationship　between　low-frequency　(LF)　features　and　sub-band　envelope　of　HF　components.　In　addition,　the　fine　structure　of　HF　components　which　can　guarantee　the　timber　of　the　extended　audio　signal　is　reconstructed　based　on　nonlinear　dynamics.　The　objective　and　subjective　test　results　indicate　that　the　proposed　method　outperforms　the　reference　methods.