The significant structure theory of water is applied to the shock-compressed water to obtain theoretically the Hugoniot adiabatics and temperatures. To consider the effect of pressure and temperature, an expression for the sublimation energy term appearing in the theory is derived using the spherically averaged Stillinger-Rahman ST2 potential, and the Gruneisen parameter is used for the Einstein characteristic temperature. Fairly good agreements are obtained in such an extreme condition of shock-wave.