In the Late 1890s – Early 1900s with the construction of the Trans-Siberian railroad in Siberia the process of intensive modernization began, which caused radical changes in society. Those changes could not but affect the institution of the family. This article gives the results of the study of the small nuclear family of workers in Western Siberia in the late 1890s – early 1900s on the basis of the quantitative characteristics data – population and family size, as well as marital status and marriage rate. The study found that the late1890s – the early1900s witnessed the growth in the share of working families with 1-5 members and the decline in the proportion of families with more than 6 members. The decrease in the proportion of families with one married couple, the increase in the number of families with two or more married couples and no couples at all, as well as certain increase in the population of the family in the 1920s observed as the indicator of the marriage rate, resulted from unfavorable socio-economic conditions and were of temporary nature without challenging the general regularities of quantitative reduction of family and formation of new marriage behavior pattern.