Abstract: To describe the wave velocity of seafloor sediments, two composite parameters that are the ratio of density variation to density (RDVD) and the ratio of the elastic modulus variation to elastic modulus (REMDEM) are introduced in this paper. The RDVD is one composite parameter which is consisted of porosity, density of solid-phase and water density, and the REMDEM is another composite parameter which is expressed by porosity, bulk modulus of solid-phase and the bulk modulus of seawater. Sound speed formula can be expanded to Taylor power polynomials of the two composite parameters above. The two composite parameters vary to constitute a sound speed surface, and the surface contains the whole information of acoustic characteristics and sediment physical properties. A porosity-sound speed function is a curve on the sound velocity surface. Numerical calculation and comparison of test results show that: if the empirical formula of porosity-sound velocity of is converted to a reference sound velocity multiplied by a standard form of modulation function, the modulation functions empirical formula of porosity-sound velocity from various sea zones are quite close each other. The difference between the formula of sound speed in the papers and Wood one is in elastic modulus model.