Abstract: In this paper, a stable wavenumber-integration method for sound field calculation in the shallow-water environment with a negative thermocline is proposed. The coefficient matrix of sound source in different water layers is obtained by normalizing Airy function. The coefficient matrix is unconditionally stable and can provide an accurate numerical solution of sound field in the shallow-water environment with a negative thermocline. Combined with a simulation instance, the calculation results of this method are compared with those of un-normalized Airy function, and the results show that the acoustic field calculation by the latter method is not accurate under some circumstances, however, the method proposed in this paper offers a good solution for this problem. Meanwhile, the comparison of the calculation results of this method with those of KRAKENC normal-mode indicates that the numerical model proposed in this paper can be used as a standard model for sound propagation in the shallow-water with a negative thermocline.