The invention discloses a clamping mechanism capable of detecting materials in a pipe cutting machine. The clamping mechanism comprises a fixed clamping block and a movable clamping block which are positioned above an operation platform as well as a drive oil cylinder capable of driving the movable clamping block to move and a PLC, wherein a charging end and a discharging end of the movable clamping block are separately provided with a detecting device; the two detecting devices are the same in structure; each detecting device structurally comprises a roller positioned at the charging end or the discharging end of the movable clamping block, wherein the roller is mounted at the outer end of a rocker arm, the rocker arm is hinged on the movable clamping block, a spring seat and an induction switch are further mounted on the movable clamping block, the induction switch is electrically connected with the PLC, an induction plate capable of being matched with the induction switch for induction is arranged on the rocker arm, a spring is arranged between the spring seat and the rocker arm, and the roller on the rocker arm is protruded out of the inner side clamping surface of the movable clamping block under jacking action of the spring. The clamping mechanism has the advantages of saving labor power and improving the working efficiency.