Present work devoted to studying of formation mechanisms, growth kinetics and coalescence of polyphase composite particles in Al-Li alloys and to their influence on alloys properties. The results obtained by research of Al-Li-Sc, Al-Li-Mg-Sc, Al-Li-Cu-Sc, Al-Li-Cu-Zr alloys aging are represented. Composite particles of two types was explored. The first type particles consists of two isomorphous phases ordered on type L1(2). Kernel is refractory intermetallide of Al3Li type, where X is Sc, Zr. A shell is metastable delta' (Al3Li) phase. Such particles of (beta'/delta' type can be formed with other transitional elements (Hf, Ti, Ta) in kernel. Metastable beta' phase is observed, like during alloying by Zr. Alloying by Sc enables to get the greatest volume part of such composite beta/delta particles, a kernel of which is a stable Al3Sc phase. Cause of composite particles formation are processes of Li absorption on interfacial surface of Al3Sc particles. There are delta' phase particles arises in layer enriched by lithium during the aging in the metastable delta' phase existence domain. In coalescence process they stick together and will make a continuous shell. Shell formation and growth occurs more intensively in the process of (beta/delta' forming, then in the process of (beta'/delta' particles with Zr forming. Interaction of composite particles with homogeneous delta' phase particles, which arises in matrix during takes place. As result of prolonged aging at the time of aging coalescence all delta' phase that present in matrix pass into shell of composite particles. Composite particles presence in alloy enables to raise stability of structural states during natural aging and strength and plastic properties of alloys. Volume part of composite particles increasing possibility due to Sc solubility rise in matrix during quenching from liquid state was examined. Composite particles of second type are combination of non-isomorphic phases - tetragonal Theta' ( Theta") phase and f.c.c. ordered delta' phase. These phases are forming during the Al-Li-Cu alloys aging. There are two sorts of these particles was observed. Superfine spherical Theta"/delta' composite particles takes place, when all delta' phase that present in matrix goes into composite particles. These particles formation mechanism connected with Theta" phase particle precipitation process in 6' phase particle. This structural state corresponding to the most favourable combination of durability and plasticity was observed during long-term low-temperature aging. As the aging temperature rises the platelet Theta"/delta' particles and homogeneous particles of 6' phase exist in matrix. It was shown the effectiveness of double-step processing for the purpose of Theta"/delta' particles volume part augmentation.