Abstract: A connection device for connection with an opening of a fluid container includes a cylindrical hollow part on which an expandable member, a movable member, a rotatable member and a handle is connected in sequence. The user holds the handle and operates a wrench to rotate the rotatbale member which moves the movable member to compress the expandable member. The expandable member is expanded to firmly engage with an inner periphery of the opening of the container such that the connection device can be well positioned when in operation.