Numerical method is adopted to analysis the tendency of cracking layer during the laser cladding on tooth surface of helical gear. The results show that a high temperature gradient generates in the cladding layer and mostly concentrates in the tooth root. It turns to be a tensile stress, so the cracks will be easily in tooth root. Cracks will generate in tooth root and extend to the outside surface along the direction of perpendicular to scanning direction. Double scanning technology is put forward to solve this problem. Calculation results show that the tensile stress in cladding layer is significantly decreased using this technology and the area that stress concentrated inside clad coating can also be reduced. Therefore, the distribution of stress field inside clad coating can be improved radically, and it is quite beneficial for cracking controlling. Teeth surfaces are clad by different scanning methods and laser parameters in experiment. The results show that double scanning technology is benefit for controlling the cracking of cladding layer on tooth surface, and reliable parameters fit for laser cladding on tooth surface of helical gear are verified according to the results.