With respect to the whole of two elemental waves in ocean surface, capillary and gravity waves, a deterministic, rich and fundamental theory of 3-4-5-wave resonance and conservation for ocean surface waves in a finite depth is developed, which presents fully the preciseness, symmetry and completeness as compared with a variety of the classical, modern results, and provides an indispensable basis for the succeeding and universal statistical theory of ocean wave turbulence.