The purpose of researches was the definition of an optimum dose of an antioxidant of Bio-50 and studying of its influence on formation of reproductive function of repair pigs. For achievement of the purpose of researches 5 groups of analogous pigs of up to 25 heads in each group were created. The control group received the diet accepted in economy; animals of 2, 3, 4 and 5 experimental groups besides the main diet received an antioxidant of Bio-50 in a dose 0,25 mg/100 kg body weights; 0.50; 0.75 and 1,00 mg/100 kg respectively. The preparation was given to pigs daily during the period from 82-84 days of age before fruitful insemination. The drug was injected in the structure of forage by manual mixing just before feeding. As a result of researches it was found out that an optimum dose of Bio-50 was 0,5 mg/100kg. Application of a preparation in the specified dose reduced terms of sexual function approach by 6.2 %, the duration of an estrus was for 17.6 % and accelerates manifestation of the first signs of hunting was for 11 days. Besides in the animals receiving an antioxidant of Bio-50 in a dose of 0.5 mg / 100 kg the fertility percentage from the first insemination increased by 8 %. The conducted researches allowed drawing a conclusion that an optimum dose of an antioxidant of Bio-50 was 0,5mg/100 kg of live weight. Application of this preparation daily during the period from 8-84 days of age before fruitful insemination allowed to reduce the terms of the first sexual signs manifestation in repair pigs and duration of an estrus during manifestation of a follicular phase of a sexual cycle. Bio-50 accelerates a sexual and economic maturity of repair pigs and raises fertility from the first insemination.