The purpose and the significance of orientation to scanning plane of the automotive adaptive cruise control（ACC）radar are pointed out based on the basic principle of the scanning laser radar and the working demands of the ACC.Through scanning the two punctual objects and the inclined plane of a cuneiform block

the depth of scanning tens

that is

the laser probe in the optic protecting cover and the height of laser scanning plane are confirmed.The complementary tests prove that the error of the test results above is smaller than 1cm

which can help to make sure the ideal installing position of the laser radar in the car

reduce the system errors and avoid the misinformation of the ACC system.