A soft ring addresses issues, such as casing deformation, waterproof capacity, and dust control. The soft ring is configured for use with a casing of an electronic device, and the casing has a first housing and a second housing coupled together. A ring-shaped receiving groove is disposed on the first housing for receiving the soft ring and a ring-shaped flange is disposed on the second housing for pressing the soft ring along the coupling portion of the first housing and the second housing. The soft ring is characterized in that a channel is disposed along the soft ring. The soft ring advantageously features a high compressed capacity and a low reaction force to thereby prevent the casing from deformation and improve the waterproof capacity and dust control of the casing.