With the purpose of comparing the differences of reflective index structure constant measured from angle of arrival and from scintillation effects, an experiment of laser propagation in atmosphere is conducted at a distance of 890 meters in the horizontal path. Scintillation index and variance of angle of arrival fluctuations are applied respectively to deduce the refractive-index structure constant in weak turbulence. The measurement results indicate that there are some differences between the two results, but the overall trends remain the same. The reason for the differences is analyzed quantitatively from two perspectives: the frequency response characteristic of refractive index fluctuation and the effect of the change of inner and outer scales on measuring. The simulation results show that scintillation is more easily affected by large scale turbulent vortexes, but angle of arrival （AOA） fluctuation is more sensitive to small turbulent vortexes. The change of inner scale has a greater influence on the result of scintillation measuring; while the change of outer scale has a larger effect on the result of the arrival-angle fluctuations measuring. The result of the arrival-angle fluctuation measuring reflects the change of large scale turbulent fields, while the result of scintillation measuring reflects small scale turbulent fields.