The utility model discloses a cable conduit blocking device which comprises a front disc and a rear disc. The front disc and the rear disc are oppositely arranged and can be placed in a cable conduit, a connecting block is arranged between the front disc and the rear disc to connect the front disc and the rear disc so as to form an integrated structure, a polyurethane foam joint mixture filling space is formed between the front disc and the rear disc, and a jetting hole communicated with the filling space is formed in the rear disc. The cable conduit blocking device has the advantages of being good in sealing effect and convenient to dismount.