The basic soil indicators were determined – pH, humus, mechanical composition of subtypes cinnamon forest soils in the region of Stara Zagora. The relationship between them was searched for through the methods of regression analysis. In the present study data for pH, organic carbon content, organic nitrogen, available phosphorus, potassium content and clay content for 47 soil samples were used (Gleic Chromic Luvisols). The studied soil samples were characterized by an acid to alkaline reaction with a wide range of pH (H2O) values between 5.9 and 7.6, the average value was 6.6, the clay content between 38.0 and 45.0 %, with low to high humus content – between 1.25 and 5.4% and from low to high organic nitrogen content – between 6.6 and 60.20 mg/kg with an average value of 30.36. A high correlation between the organic nitrogen content, mg/kg and K2O, mg/100 g with R=0.64 (Fig. 3) was found; between the humus, % and organic nitrogen content, mg/ kg with R = 0.58 (Fig.4) and between the humus content and K2O, mg/100 g with R=0.55. A low correlation between the available phosphorus and potassium with R<0.33 was established. On the basis of humus, % and pH values for soil samples a principal component analysis was performed to understand the distribution of soil samples in multimensional space. Five clusters (groups) were specified in advance. After performing the factor analysis it was found that 86.62% of the variations of pH values were based on the modification of the content of humus. A statistical model for the relationship between humus and pH was developed.