The author has analyzed the composition of the Southern Ukraine population on its native language, examined the peculiarities of the linguistic structure of the population in some districts as well as urban and rural settlements in the region; carried out the comparative analysis of the ethnic and linguistic structures of the population, determined the level and nature of language assimilation processes in the region and in the Ukrainian SSR in general.The results of the study suggest that in 1926 the vast majority of the population of Southern Ukraine considered Ukrainian language as its mother tongue. The analysis of the linguistic structure of the population of some districts in Southern Ukraine showed that the Ukrainian language prevailed in most of them, except for Odessa district. Russian language, which less than a quarter of the population acknowledged as their native language, was the second demographic capacity language in the region. However, it had more communicative power and, as a result, more assimilation potential than Ukrainian language. This was also determined by the fact that Russian language was the official language of the USSR. The languages of other peoples living on the territory of the region generally played a minor role in its linguistic environment.The comparative analyses of ethnic and linguistic structure of the population of Southern Ukraine showed that the Ukrainians, notwithstanding their numerical majority, have implemented insignificant assimilative influence on other ethnic communities of the region. Moreover, they themselves have suffered assimilation from the Russian ethnic minority. All the above mentioned allowed to make the conclusion about the asymmetric and unnatural character of the assimilation processes in the region. The Russian assimilative influence manifested itself mostly in urban settlements – administrative, economic and cultural centres of the South of Ukraine. In small towns and rural settlements, the process of Russian assimilation happened slower and for majority of population Ukrainian language was the mother tongue.However, in general, the Russification on the South of Ukraine in 1926 did not acquire threatening character and for the vast majority of population the native language was the language of its nationality, the assimilation processes in the region happened more intensively than in the Ukrainian SSR in the whole.