A liquid cooled motor assembly and a cover thereof The cover of the liquid cooled motor assembly has an outer cylinder, an inner cylinder, a channel and multiple fins. The inner cylinder is mounted in and connected securely with the outer cylinder. The channel is zigzag and is formed between the inner cylinder and the outer cylinder. The fins are mounted securely on an outer surface of the inner cylinder. With the fins mounted on the outer surface of the inner cylinder, water can dissipate heat from the fins quickly and a dissipating efficiency is enhanced.