The invention relates to an obstacle detection sensor for a robot. The obstacle detection sensor is characterized in that the robot is provided with at least one linear laser emitting device facing ground ahead; positions at the front portion of the robot, which are lower or higher than the linear laser emitting devices, are provided with at least one digital imaging module; the digital imaging modules are mainly used for capturing projection lines of linear laser beams at projection positions in front of the robot onto the CCD or CMOS photosensitive elements of the imaging modules; whether the projection lines of the linear laser beams on the ground are blocked by an obstacle can be judged according to the positions and shapes of the laser beams on the photosensitive elements; and the linear laser emitting devices are a plurality of small-field angle linear laser emitting heads which are arranged side by side on the same plane. With the plurality of linear laser emitting heads adopted, a coverage range in front of the body of the linear leaving robot can be extended, and therefore, the obstacle detection sensor is advantageous in larger coverage range compared with an obstacle detection sensor adopting a single linear laser emitting head.