The cutback film cooling was important to decrease the trailing edge temperature and prolong the working life of gas turbines. Many investigations concerning cutback film cooling have already been done. However, only a few papers involve the influence of incident angle on the film cooling effectiveness (η) at the trailing region. In this work, detached eddy simulation (DES) is applied to calculate the η near the cutback region for different incident angles. Five different incident angles (0 deg, 5 deg, 10 deg, 15 deg, and 20 deg) and three blowing ratios (0.2, 0.8, and 1.25) are considered. The flow structure, temperature distribution, and η characteristics are analyzed in detail. Results imply that the incident angle changes the flow structure notably. As the incident angle increases, the separation region is suppressed, but the η was changed nonlinearly. At the low blowing ratio, the incident angle mainly affects the η near the slot. However, the incident angle changes the η downstream of the slot exit under a high blowing ratio. When the blowing ratio becomes large, the η near the centerline becomes larger.