The invention of the group discloses a method for welding a top reinforcing plate of a container and a welding robot thereof. The method includes the steps: position detection of work pieces, a first distance sensor, a second distance sensor and a third distance sensor are selected, wherein the first distance sensor and the second distance sensor are arranged on the X axis or the Y axis of a horizontal coordinate, the third distance sensor is arranged on the other axis of the horizontal coordinate, and the work pieces to detect are arranged on areas which can be detected by the three distance sensors; firstly, the initial positions and the types of the work pieces are obtained, secondly, the information of other inflexion point is obtained, and thirdly, the trajectory planning of a weldingseam can be formed through synthesization; and according to the trajectory planning of the welding seam, a welding torch is controlled to move along the edge of each work piece to accomplish the operation of welding. The welding robot is provided with a welding seam position automatic recognition mechanism, a welding torch posture automatic adjustment mechanism and an automatic welding mechanism.The method and the welding robot are especially applicable to the automatic welding of the top reinforcing plate of the container.