A joint includes a male module and a female module capable of docking with each other. The male module includes a core rod and a sliding cylinder that is slidably sleeved on an outer periphery of the core rod. A first valve port is disposed in the sliding cylinder, and the core rod is provided with a piston head that is in hermetic fit with the first valve port. The female module includes a valve body and a piston. A first channel is disposed in the valve body, the piston is slidably disposed in the first channel, and a second valve port that is in hermetic fit with the piston is disposed in the first channel.