<p>This paper presents theoretical and experimental studies on the nonlinear vibration characteristics of conical shells with bolted flange boundaries. A nonlinear mechanical model of the bolted flange boundary considering amplitude-dependent stiffness and damping at the connection interface is established. Theoretical modeling utilizes Donnell's shell theory along with the displacement assumptions based on Chebyshev polynomials, leading to the derivation of the governing equation using the Lagrange equation. The modal and response testing platforms are constructed, and after validating the frequency response under different tightening torques, the effects of bolt loosening on the nonlinear vibration response are analyzed through theoretical calculation combined with experimental validation. The amplitude-frequency results indicate that the bolt loosening leads to an initial increase followed by a decrease in the resonance response, as well as a leftward shift of the resonance frequency, which can be attributed to the combined effects of contact state and connection stiffness at the bolted flange interface. By comparing the vibration responses under various bolt loosening boundary conditions, the study provides insight into the role of frictional sliding and stiffness degradation in nonlinear vibration behavior, offering a foundation for the dynamic prediction and design of bolted structures in engineering applications.</p>