Backcross introgression lines are genetic and breeding materials constructed by backcrossing andmarker-assisted selection. After multiple backcrossing, the progenies only contain one or a few chromosome seg‐ments of the donor parents in the genetic background of the recurrent parents, so they can be used as important ma‐terials for QTL analysis. At the same time, multi-generation backcross is beneficial to break the linkage between ex‐cellent gene and bad gene, and good gene is introduced into the recurrent parent material with good performance,and further improve breeding material. In view of their consistent genetic background, introgression lines play an im‐portant role in fine mapping and gene cloning, QTL interaction, genetic validation, crop pyramiding breeding andbreeding by molecular design. In this paper，the advanced progresses on the construction and application of CSILpopulation in crop were reviewed.