Abstract: The horizontal random perturbation on a qudsi-plane wave field in a random channel was treated as a stationary Gaussian process. The degradation of horizontal coherence in shallow water homogeneous layer due to the influences of micro-structure of water masses and random boundary was calculated for field region of "three-half":\beginarrayl R(\infty ) = \exp - Ak_0^2,\\ A \equiv \left \sqrt \pi \mu ^2 ar + 0.3\frac\sigma _H^2Q^2.5\rm\cdot\left( \fracH_0r \right)^1/2 \right, \endarrayherek₀ is wave number ;\overline \mu ^2 and a are parameters of micro-structure, O²_H is the standard deviation of the fluctuated boundary,H₀is the average water depth, r is the transmission range and Q is the parameter of bottom loss.