Abstract: In order to solve the problem of digital radiography for printed circuit board(PCB) defect inspection, an examination system was introduced for PCB defect inspection with high resolution X-ray. Through analysing the influence of the focus size of X-ray source to imaging formation, the best geometrical magnification was got. Analysing on performance of MCP-X intensifier, the relationship between the resolution of intensifier and geometrical magnification was deduced, and then we could calculate the comprehensive resolution of this system. Through the examination, it was concluded that, the system realized the measurements on defect character, the measuring accuracy to the BGA solder joint of circuit board was reached to 0.03 mm, meeting the request of inspection on invisible solder joint.