Y tube anti-pollution method and its apparatus

The invention discloses a Y tube pollution-prevention method and a device thereof. The method comprises the following steps: (a) descending an underground switch to the preset position through a salvage tube and then lifting up the salvage tube; (b) sleeving the docking and sealing tube onto the underground switch from bottom to top sequentially, and connecting the upper part of the tube with holes with the Y joint that is provided with an electric pipe unit and a production blocking device; (c) lifting the docking and sealing tube after washing the well circularly to break the docking and sealing tube away from the underground switch, and the baffle on the underground switch closes automatically and stays in the well to avoid the well-washing liquid from leaking into the stratum. Compared with the method relying on casting and salving blocking device, the Y tube pollution-prevention method avoids the problem of being unable to salvage the pollution-prevention blocking device and increases the reliability of the technology.