The invention discloses a sealing device applicable to a three-way pipeline. A lug plate, a fixed ring and a sealing box are included; the lug plate comprise a first lug plate body and a second lug plate body; and the first lug plate body and the fixed ring, the fixed ring and the sealing box, and the sealing box and the second lug plate body are welded together. According to the sealing device, the fixed ring is fixed to a main pipe needing to be sealed, a proper amount of sealant is injected into the sealing box through a glue injecting hole and a glue injecting channel, and therefore a leaking point is sealed, the leaking point of the three-way pipeline can be controlled under the condition without shutdown, and it is avoided that due to pipeline leaking, production shutdown is caused,and huge waste is caused to an enterprise and safety accidents are caused.