The invention discloses a method and system for calculating an included angle between a truck head and a trailer by using a laser point cloud. A laser radar is arranged at a truck head and point clouddata obtained by scanning of the laser radar are collected and stored in real time; according to a distance range between an edge line of the trailer and an original point of the laser radar, a pointcloud that is obtained by scanning the edge of the trailer by the laser radar is screened out from self-stored point cloud data; a three-dimensional point cloud of scanning the edge of the trailer isprojected to an XY two-dimensional plane to obtain one beam of point set; on the basis of the principle of least squares, the one beam of point set projected on the XY two-dimensional plane is fittedinto a straight line; and then an included angle between the edge of the trailer and the axis of the truck head is calculated based on the slope of the straight line, so that an included angle between the truck head and the trailer is obtained. Therefore, only the trailer edge line point cloud scanned by the laser radar at the truck head is used for processing and no extra auxiliary device is needed; and since the regional limitation of the geographical conditions is eliminated, the method and system have the large application range.