The breeding program of Giza 45 was conducted at Sakha Agricultural Research Station, Kafr El-Sheikh district during 2011 to 2014 growing seasons. In 2011 season 42 type plants were selected from the breeding field of Giza 45 variety and furnished 42  progenies (increase A) in 2012. From the latter, fourteen  families were selected to descend (increase B) in 2013. According to the statistical analysis of yield trial which include the fourteen families and comparisons of the latest lines of Giza 45, four elite families were selected and the seeds were carefully massed together to form the nucleolus (breeder's seed) in 2014 season. The results obtained here indicated that, the pure line method in the sense of pedigree selection for renewing annually Giza 45 breeder's seed could produce high genetic pure seeds and in the same time, prevent genetic contamination. Meanwhile, the selection technique for producing breeder's seed of Giza 45 variety was valid and proved to be effective in holding this variety according to the standard type of Giza 45. Genetic purity, Maintenance ,cotton nucleolus .