The propose of this work is to identify the isotopic ratios and their variations for uranium-238 series isotopes in some collected phosphate samples and experimental examination of 186 keV gamma line separation method and also to study the effects on these values to investigate and interpret the distribution of radionuclides and check the secular equilibrium in uranium decay series. These results will contribute to a better understanding of the behavior of radionuclides during the development of the phosphate industry in the El-Sebaiya area. The isotopic activity ratios of 238U/235U, 238U/226Ra, 226Ra/214Bi, 226Ra/214Pb, and 214Pb/214Bi have been calculated, and the phosphate sample was analyzed using a hyper-pure germanium detector. The analysis of the spectra was done using GammaVision analysis software. The samples were collected from El-Sebaiya locality, Aswan, Egypt.