Large-size echelle grating can have extremely high spectral resolution due to its large aperture and high diffractive order. To achieve high-performance large-size echelle grating, the preparation of high-quality aluminum film with large-area uniformity is one of the most important factors. In this paper, for the first time so far as we know, we report the preparation process of high-quality aluminum with large-area uniformity in details. First, we simulate theoretically the influence of the position and emission characteristic of the evaporation source, as well as the fixture height, on aluminum film uniformity. Then, we study the influence of some key parameters of the evaporation process (such as the evaporation height and rate) on aluminum film quality and uniformity. Finally, under the optimal conditions, we prepared successfully the high-quality aluminum film with its thickness being larger than 10 m and uniformity fluctuations less than 1% within a diameter of 700 mm.