Complex diseases are the any ones that there is no classical mendelian dominant or recessive inheritance model for a single locus. And cancers are a kind of common complex diseases. Based on the linkage analysis and association analysis, many genetic mapping approaches of complex diseases had been grown up such as functional cloning, candidate cloning, positional cloning, positional candidate cloning and systems biology approach and so on. Among them, systems biology approach is in the ascendant now. Because it integrates all of the informations from DNA to proteins, it gives a better commentary of the complicated gene- regulatory network. This advantage makes it become one of the most potential methods in the 21 century. Nearly one hundred of cancers had been mapped so far. Furthermore, the genetic mappings of complex diseases still shoulder heavy responsibility.