Emotions have a significant impact on the physiological processes in the body of an athlete. It is obvious that the levels of mental stress of an athlete during training, participation in competitions and recreation are not the same. Given the well-known predisposition of athletes to alexithymia, there is a need to search for objective ways to assess the level of psycho-emotional stress. Our work evaluates and compares the differences in the psycho-emotional state of athletes in various phases of the annual macrocycle using the calculated Stress Index (SI), based on electroencephalogram indicators. The study involved 155 athletes, representatives of various sports. Male - 96 athletes, average age 24.34 ± 3.54 years; female - 59 athletes, the average age was 23.12 ± 2.3 years. The control group consisted of 101 people who did not experience systematic high physical exertion. Male 53, average age of 23.17 ± 2.54. Female – 48, average age of 22.12 ± 3.01 years. The values ​​of SI in athletes are significantly different from those in the control group, as well as among themselves at various stages of the annual macrocycle. In the preparatory and transitional periods, the SI is significantly lower than in the control group, however, during the competitive period, this figure increases significantly, which characterizes a significant increase in psycho-emotional stress among athletes. There is a high positive correlation (r = 0.81) between the SI value and the number of points scored in the Spielberger-Hanin situational anxiety test.