The availability of the saturated DNA marker maps in livestock has made it possible to locate quantitative trait loci (QTL) in these domestic animals. The objective of this research was to investigate the principles of applying the simple regression for QTL analysis in paternal half-sib (PHS) design commonly used in livestock species. The theoretical aspects of the simple regression approach for QTL mapping in PHS design were studied. Simulation study showed that the power of QTL detection using the regression method increased as the sample size and QTL effect increased. Also increasing family size led to improved precision and accuracy of QTL parameters (estimates of QTL location and effect). The experimental beef cattle weaning data recorded on 366 animals from three half-sib families genotyped for 189 microsatellite markers were analyzed exploiting the simple regression approach. The results revealed two large QTL affecting weaning weight. The two detected QTL were located on Bovine chromosome 14 (BTA14) and (BTA16) at 29 and 81 cM, respectively.