The article discusses theoretical aspects of integration approach to the study of the development of the agrarian sphere of economy. The article presents authors who have made significant scientific contributions to the theory of integration; identifies structural elements of the national agro-industrial complex; determines the value of scientific and technological progress in the development and integration of productive forces; identifies factors affecting the development of the agrarian sphere as a complex integrated system. The article notes that integration as a system possesses characteristics of self-organization, hierarchy, striving for equilibrium, and has the presence of a common goal. The article particularly characterizes the socio-economic factors of integration, influencing the agricultural sphere development and management. Particular emphasis is placed on the problem of integration of Russian agricultural industries in the WTO.