In order to gain a clear idea of the range of OTHR first-order sea clutter backscattering coefficient and its changing law on the whole and also the change discipline of the first-order sea clutter backscattering along with the affection of OTHR frequency, wind speed on sea surface, angle between the directions of ocean wave and wind, and the spread degree of wave height spectrum with direction about the wind direction on ocean surface, considering the characteristic of OTHR detection, the paper introduces the first-order sea clutter backscattering coefficient model given by Barrick, and then, by means of simulating, obtains that the first-order sea clutter backscattering coefficient is within if the non-directional amplitude spectrum is in the state of saturation or within if the non-directional amplitude spectrum is in the state of unsaturation, in addition, the magnitude of the frequency and of the speed of wind on sea surface determine that non-directional amplitude spectrum is in the state of saturation or in a state of unsaturation. And then also through simulating the affection of every parameter on the first-order sea clutter backscattering coefficient, the paper presents the change discipline of the first-order sea clutter backscattering along with each parameter. All these are useful to OTHR detecting and father high frequency radar sea clutter modeling and filtering.