The problem of a nationality (national character) in the Russian literature, in particular, in creativity of the Russian writer of the end XIX – the beginnings of XX centuries – A. I. Kuprin is considered. The nationality (national character) of a vital and creative position of the writer is fairly regarded as conducting force of his talent. The purpose of given article is to prove, that A. Kuprin's national psychology investigates in the different social validity: in the army environment, in the country environment. In this connection works of the writer about army life are analyzed: stories “Night shift”, “Inquiry”, the story “Duel”. Cruelty of the army environment, the brutal attitude to soldiers are marked. Images of soldier Merkulov and of soldier Zamoshnikov from the story “Night shift” are analyzed. Comments on author's sympathy to simple people are given. The second part of article is devoted to the analysis of works of A. Kuprin about peasantry. Particularly detailed analysis of the author's Polessky cycle is, which included stories “Forest wilderness”, “On wood grouse” and the story “Olesya”. The peasantry of A. Kuprin is shown from the negative side, commotion, ignorance, laziness, drunkenness of the peasants. Most vividly Kuprin wrote out the images of Cyril and Talimon from the story “Forest Wilderness” and the image of Yarmola from the story “Olesya”. The characteristic features of the images are illustrated by examples from the texts of stories and novels. In addition, it is noted that the images of Cyril, Talimon, Yarmola are no exception, but, on the contrary, their connection with the rest of the village world is emphasized. In conclusion, the article concludes that Kuprin's work was always connected with the life of the common people, and people's characters are always shown in the context of social reality.