A phenotype evaluation of the change in the body construction of the autochthonous Bulgarian Gray Cattle Breed reared in ‘Strandzha’ breeding region was carried out in the herd of SCA- Sredets. 10 exterior measurements and 8 body construction indexes were assessed as an element of the process of biodiversity preservation. The study was conducted on the basis of 34 full records of adult cows. The measurements of the animals were taken in 2004 and 2019 upon their bonitization. The experimental data were processed via ANOVA single factor in the medium of the SPSS program product. The exterior measurements of the controlled animals are close to those of the breed updated standard. The fully mature cows of the modern population of the herd have a wither height of 120.8±2.02cm, athwart body length of 144.6±2.42 cm, chest girth of 168.3±2.07 cm and cannon bone girth of 16.3±0.15 cm. The changes within the population over a 15-year breeding period have indicated light-weighting of the type, and chest parameters which have become lower (0.05>P<0.01). The cows from the modern population have lower values regarding the chest (5.14%) and the pelvic- chest indexes (8.97%) which leads to a lower body massiveness (-7.21%) (P<0.05).