1. A method for smart defect screen and sample, comprising: pre-processing a design layout of a product into a plurality of layout based pattern groups, wherein the design layout has a plurality of layout patterns; dividing the design layout into a plurality of cells, wherein each cell belongs to a layout based pattern group according to the layout pattern's feature; overlapping the cells belong to the same layout based pattern groups; extracting a plurality of defect data of all defects on a wafer from a defect scan and inspection tool, wherein each defect data comprises a defect size and a defect coordinate; constructing a plurality of layout based defect composite pattern groups by mapping the defects onto the overlapped layout based pattern groups; executing layout pattern match to obtain each individual layout based defect composite pattern group if original layout based defect composite pattern group contains more than one defect cluster layout pattern; performing some defect sample selection rules to each layout based defect composite pattern group for judging a potential systematic defect priority; sorting the layout based defect composite pattern groups into different defect types according to the potential systematic defect priority; obtaining a defect image file by reviewing different sample number of defect image from each layout based defect composite pattern group according to the defect types; and generating a defect pattern library or a defect yield prediction by performing a defect yield diagnosis to the defect image file.