Abstract: Based on the covering-domain method, an expression for calculating the interior scattering sound field of an arbitrary-shaped closed thin shell in which there are some scatterers. The conclusion can be obtained that the interior scattering sound field can be expressed as the superposition of the interior scattering sound field of the arbitrary-shaped closed thin shell and the external scattering sound fields of these scatterers. At last the conclusion is verilied by the corresponding numerical calculations.