Abstract: Methodology for determining the position and effects of a QTL linked with a segregation distorting-locus (SDL) is presented in this paper. The maximum likelihood estimates of the recombination fraction and the viability of gametes are determined using markers showing segregation distortion in backcross populations. And the estimates of the position and effects of the QTL are obtained using interval mapping method in an additive-dominance model. This method can be used to analyze those markers showing distorted segregations,which may be discarded in conventional mapping studies,and may help us find some new SDL (or sterile gene) and QTLs.