Flexible mouth cup

The utility model provides a portable flexible mouth cup which is composed of a cup cover (1), an inner cup (2), a water-proof device (4), an out cup (5) and a cup bottom (6), the cup cover is set on the inner cup (2) top, the inner cup (2) is set in the out cup (5) inside, a down part of the inner cup (2) is set with outside screw, an upper part of the out cup (5) is set with inner screw, the inner cup (2) screw joints with the out cup (5), the cup bottom (6) is set on the down part of the out cup and integrates with the out cup (5), an out edge of the cup cover (1) has same diameter with the out cup (5). The flexible mouth cup has no special requirement to the cup body material and size, and has simple manufacturing process. The mouth cup has the water-proof device which can prevent leakage efficiently, also can reduce space, convenient to carry and is suitable for going out to travel and field marching.