Measurements of residual stress in beryllium thin film under standard Bragg-Brentano geometry are always problematic. In this article, a new experimental method using grazing- incidence X-ray diffraction is presented according to the convential sin2Ψ method, which effectively increases the signal-to-noise ratio. Analysis shows that the assumption (isotropic material) is logical, because the values of stress results from the three families of planes are camparable. The stress gradient can be measured at diffrenent grazing incidence angles. The results indicate the uniformity of the residual stress of the thin film along various Φ directions.