The article is the first part of the work devoted to the study of the specifics of the “Parnassian” sonnet. The purpose of this article is to formulate the problem and study it in the first approximation using the material of the sonnet works of Ch. Leconte de Lisle. Twenty-three sonnets and one sonnet poem were examined, the writing strategies of the French poet were studied; the thematic range of the sonnets, the scheme and pattern of their rhyme were analyzed. The transformation of the sonnet as a genre and as a form was studied using the material of the sonnet poem "Le Conseil du Fakir". The study revealed the characteristic features of the poet's writing strategy: the arrangement of poetry collections mostly from previously published texts; the author's editing of the text is possible after its first publication, as well as constant editing of the composition of the poetry collections themselves. The thematic range of Leconte de Lisle's sonnets is quite wide and includes philosophical, landscape, animalistic, orientalistic sonnets, etc. It is concluded that the outwardly classical, traditional sonnets of Leconte de Lisle are original in their scheme and rhyme pattern. In the poem "Le Conseil du Fakir" Leconte de Lisle uses only the sonnet form. A preliminary conclusion is made that Leconte de Lisle, like his romantic predecessors (Sainte-Beuve, Nerval), "shakes" the sonnet canon at different levels: expansion of themes, content and structure.