A robot mower for moving and working in a working scope determined by a limit comprising: a housing having a longitudinal central axis; a driving module for driving said robot mower to move and to make turns, being mounted in said housing, said driving module comprising a wheel set and two driving motors for driving the wheel set to move; a limit detecting module being mounted in said housing comprising border sensing elements respectively located on two sides of said longitudinal central axis, said limit detecting module for detecting one of said border sensing elements being outside a border line; an energy module for providing energy for said robot mower being mounted in the housing; and a control module electrically connected with said driving module and said limit detecting module; wherein said control module controls said driving module to perform a turning operation away from the limit, so that the turn is clockwise if the left side of the robot mower is closer to the limit or anticlockwise if the right side of the robot mower is closer to the limit, according to which of the border sensing elements first sends a signal to the control module representing that it is outside of the border line; the turning operation being performed such that if the limit is divided into one side and another at the intersection of said longitudinal central axis of said robot mower and the limit, the longitudinal central axis always forms an acute angle or a right angle with said one side of said limit when said turning operation is completed, said another side of said limit forms an acute angle or a right angle with said central axis of said robot mower when said turning operation starts; wherein during the turn the two driving motors rotate the wheels at different speeds or in different directions. a housing having a longitudinal central axis; a driving module for driving said robot mower to move and to make turns, being mounted in said housing, said driving module comprising a wheel set and two driving motors for driving the wheel set to move; a limit detecting module being mounted in said housing comprising border sensing elements respectively located on two sides of said longitudinal central axis, said limit detecting module for detecting one of said border sensing elements being outside a border line; an energy module for providing energy for said robot mower being mounted in the housing; and a control module electrically connected with said driving module and said limit detecting module; wherein said control module controls said driving module to perform a turning operation away from the limit, so that the turn is clockwise if the left side of the robot mower is closer to the limit or anticlockwise if the right side of the robot mower is closer to the limit, according to which of the border sensing elements first sends a signal to the control module representing that it is outside of the border line; the turning operation being performed such that if the limit is divided into one side and another at the intersection of said longitudinal central axis of said robot mower and the limit, the longitudinal central axis always forms an acute angle or a right angle with said one side of said limit when said turning operation is completed, said another side of said limit forms an acute angle or a right angle with said central axis of said robot mower when said turning operation starts; wherein during the turn the two driving motors rotate the wheels at different speeds or in different directions.