The uniformity of the film thickness of the aluminum film deposited by the thermal evaporation of the 1.1 m large-diameter coating machine is studied. For the rotating plane fixture， the influence of the fixture height H and the distance L between the evaporation source and the central axis of the vacuum chamber on the uniformity of the aluminum film thickness is analyzed. When L=400 mm and H/L=1.10， the film thickness uniformity is the best， the unevenness is 9.614%， and the unevenness increases as the value of H/L increases. When H=500 mm and H/L=1.47， the film thickness uniformity is the best， the unevenness is 4.487%， and the unevenness increases as the value of H/L decreases. Furthermore， a modified baffle function is introduced， and a suitable correction mask is proposed and designed. The film thickness uniformity is improved from 17.8% without the correction mask to 3.9%， thereby solving the problem of aluminum film thickness uniformity.