Abstract: It is necessary to select an appropriate integral truncated wavenumber in sound field calculation with wavenumber integration method. In this paper, an adaptive truncated wavenumber selection method for broadband sound filed calculation in fluid waveguide is proposed, which means that the wavenumber integral can be truncated at a given accuracy. A mathematical model is established to fit the attenuation characteristics of Green's function in wavenumber domain. The fitting parameters in the mathematical model are tracked and predicted by Kalman filters. The truncated wavenumber is estimated according to the mathematical model and its predicted parameters. The experimental results show that the truncated wavenumber selected by the proposed adaptive method can make the integral truncated at a given accuracy, which solves the problem that the existing methods cannot take into account the calculation accuracy at low frequency and the calculation amount at high frequency, and no much additional computation is introduced.