Purpose. To determine the patterns of change in the content of the green pigment in plant chloroplasts of sugar beet and their relationship, to identify the features of pigment complex during the growing season. Methods. Field, laboratory, analytical, and statistical. Results. The peculiarities of changes in chlorophyll content in the leaves of sugar beets during the growing season are presented. It was found that the most intense green pigments synthesis occurs in the stage of closing leaves when their content reaches the maximum value: chlorophyll а of 8.620 mg/g and chlorophyll b of 4.15 mg/g. Using the ratio of chlorophyll a and b in their total weight the accumulation of a pigment depending on the stage of plant development is determined. Thus, in the first half of the growing season (the 8-true leaves stage and the stage of leaf closure between rows) the synthesis of chlorophyll b dominates, while in the second (the stage of closure leaves in rows and the technical maturity stage) chlorophyll a. Conclusions. It was established that the least intensive synthesis of chlorophyll occurs in the early stages of plant growth and development due to small leaf surface area and low assimilation of the photosynthetically active radiation. Thus, at the beginning of the growing season crops (the 8-true leaves stage and the stage of leaf closure between rows), chlorophyll b dominates in the structure of the green pigment. Reduction of chlorophyll content 1.3 times the end of the growing season (in the stage of technological maturity – 6.3 mg/g) compared with the stage of leaf closure in rows occurs due to the accumulation of sufficient sugar supply in the roots resulting in slowing physiological processes and the dying off old leaves.