A printed circuit board (PCB) testing system includes two gear groups, a pair of transmission belts and a driver. The pair of transmission belts geared onto and driven by the two gear groups is parallel and respectively perpendicular to the PCB transmission guideway so as to define a PCB accommodation space therebetween. Each transmission belt includes a plurality of projections. The two gear groups are rotated synchronously and inversely. During operation, the projections on the pair of transmission belts, facing the PCB accommodation space, move down, the projections move away from each other and to the bottom of the corresponding transmission belts, and a PCB supported by the pair of projections drops onto the PCB transmission guideway.