Abstract: In this paper,starting out near-axis approximation and considering the correlation of intensity fluctuation,one derives a universal formula (Eq.14)of angle of arrival(AOA)fluctuation variance σ_α² under the suppositions of Markov random process.For plane and spherical wave propagation, the analytic expressions of σ_α² are obtained.Some experiment data are used to compare with analytic results. It shows that both are identical.