Recently piezoelectric shunt damping has attracted a lot of attention in vibration and noise control. In this article, piezoelectric shunt damping is used in underwater sound absorption in order to enhance the sound absorption of the coating. A one-dimensional electro-acoustic model is established for the calculation by combining the equivalent circuit of thickness mode of a piezoelectric composite coating with the transfer matrix of plane wave propagation. This model can be used to calculate the sound absorption of multiple layers of piezoelectric and non-piezoelectric mediums. Underwater sound absorption of the 0-3 type piezoelectric composite coatings is theoretically analyzed. Elastic, piezoelectric and dielectric constants of the 0-3 type piezoelectric composites are calculated by Furukawa's model. Results show that the negative capacitance circuit can adjust the surface acoustic impedance of the piezoelectric composite coating at broadband frequencies. Suitable shunt resistances can make it match the characteristic acoustic impedance of water better. Therefore, the sound absorption can be greatly promoted.