Underwater sound absorption coating is significant to the stealth of a submarine, so it attracts a lot of attention. Underwater sound absorption of visco-elastic composites coating containing micro-spherical glass shell was investigated theoretically. The mechanical and acoustic properties of the composites in response to the volume of the micro-spherical glass shell were analyzed by the effective parameters method. Sound absorption of a single layer composites coating containing different volume of micro-spherical glass shell was calculated by the one-dimensional model, in which sound propagates in multi-layer media. The calculated results show that the sound absorption at low frequencies can be promoted by increasing the volume of micro-spherical glass shell, but the sound absorption at high frequencies is depressed. The volume distribution of the micro-spherical glass shells across the thickness of the coating was optimized by the genetic algorithm. The optimal multi-layer structure can promote the sound absorption at low frequencies, and keep the sound absorption coefficients above a limited value (0.7) at high frequencies. The optimal multi-layer composite coating can work at high pressure since it does not contain hollow macro-structure. Its structure is simple, so the technique of its fabrication should not be complicated. The theoretical method achieved in this paper can be applied in the design of underwater sound absorption coating.