The atmospheric structure constant of refractive index [ C2n] is an important parameter of atmospheric optical turbulence intensity. The atmospheric coherence length of the winter horizontal path in some region is measured using the atmospheric coherence meter. In the case of approximate weak fluctuation condition, considered the average turbulence effect on the path, the relation formula between the atmospheric coherence length and [ C2n] is deduced. The profile and daily variation characteristics of[ C2n] are obtained by statistical analyzing for experimental data of winter horizontal in the region, and structure characteristics of atmospheric turbulence in the region are known clearly. The best time window for laser transmission is found by statistical results.