The article examines the transformation of the life cycle of a peasant family in Russia in the 20th century in demographical transition circumstances aggravated by multiple demographical catastrophes. The information basis of the study is databases formed during the analysis of budget surveys of peasant farms in the Middle Urals in 1928/1929 and 1963. Supplemented by information from other sources (materials from the population censuses of 1926, 1939 and 1959), these data allowed the authors to compare the family structure of the rural population of the Urals in the 1920s and the 1960s (the initial and the final stage of the demographical transition) and characterize its dynamics (the life cycle). Whereas in a traditional society the life cycle of a peasant family was largely determined by the dynamics of the peasant economy development, the urbanized society witnesses two standards of the family (two-parent/single parent one) with the corresponding types of the life cycle: the nuclear family (the reference version) and the incomplete family (the reduced version). The consequences of the Soviet modernization contributed to the transformation of fragmented forms of the family into a typical variant of the family landscape not only in urban but also in rural areas. Modeling and analysis of the peasant family life cycle at the micro level made it possible to identify the mechanisms of the peasant family adaptation to external and internal challenges that are characteristic of different stages of the demographic transition.