By comparing the method of step-and-repeat scanning with the one of hexagonal seamless scanning,which are favorably used in the laser projection imaging for printed circuit board(PCB),it is shown that the hexagonal seamless scan-repeat technology is of more superiority. It is expounded the process of uniform exposure in hexagonal seamless scanrepeat technology as well as the principle to achieve it. It is also analyzed the factors to affect scanning imaging such as exposure dose,velocity and so on.