Alexei studied trombone in music school at the N. A. Rimsky-Korsakov Saint Petersburg State Conservatory under Honored Artist of Russia G. Strautman, completed his studies in 1991. Later he continued studying trombone at the N. A. Rimsky-Korsakov Saint Petersburg State Conservatory under Honored Artist of Russia, senior lecturer B. Vinogradov and People’s Artist of Russia professor V. Sumerkin. In 2009 he passed a practical training in symphonic conducting under A. Polishchuk.
In 1991 he joined the Mariinsky company as orchestra musician. Since 1996 - symphony orchestra musician, trombone section. Since 2007 – stage orchestra conductor with the Mariinsky Theatre. He debuted as conductor with the Mariinsky orchestra in ballet performances The Rite of Spring and The Magic Nut (2007). Since that time he has been regularly conducting ballet performances, his repertoire includes ballets Anna Karenina, Apollo, Ballet #2, The Young Lady and the Hooligan, The Fountain of Bakhchisarai, La Bayadère, The Prodigal Son, The Rite of Spring, Le Spectre de la Rose, The Magic Nut, La Rose Malade (Adagietto from Gustav Mahler’s Symphony No.5), Don Quixote, Jewels, The Firebird, Giselle, Bolero Factory, Cinderella, Infra, Carmen Suite, Carnaval, The Little Humpbacked Horse, Le Corsair, Swan Lake, A Legend of Love, Leningrad Symphony, Marguerite and Armand, Park, Petrushka, Polovtsian Dances, Le Réveil de Flore, Raymonda, Romeo and Juliet, Sylvia, La Sylphide, Symphony in C, The Sleeping Beauty, Tarantella, Theme and Variations, The Dying Swan, Piano Concerto No. 2, Scheherazade, Chopiniana, Scotch Symphony, Şüräle, The Nutcracker, Etudes, Le Jeune Homme et la Mort, Concerto DSCH, Grand pas from Paquita, Inside the Lines, Pas de deux to Tchaikovsky’s music.
His international appearances with the Mariinsky company include Covent Garden (the UK), Festspielhaus (Germany), Metropolitan opera and John F. Kennedy Center for the Performing Arts; he also toured to Tokyo, Bangkok, Singapore, Barcelona, Valencia, Hong Kong. Alexei Repnikov launched organization of the Big brass ensemble. It was his idea to start an international festival Brass nights in Mariinsky, which was launched in March 2008 at the Mariinsky concert hall. He headed the Big brass ensemble at the Summer festival in Mikkeli (Finland, 2009), toured to the UK, Japan, Switzerland.