The slowdown of the machine-building enterprises' innovative development, the growth in the numbers of bankrupt enterprises, the instability of the market environment for their functioning - highlight the issues of the innovation activity's increasing of business entities and therefore this article is devoted to consideration of scientific and methodological aspects of the effectiveness' evaluation of innovation activities and the development of the economic mechanism. The article analyses the existing approaches of domestic and foreign scientists in assessment the efficiency of innovation activities of enterprises, it is determined that there is no effective methodological approach to the development of an economic mechanism that would take into consideration the achieved level of innovation development, financial and economic activity. The methodological approach to the development of the economic mechanism is improved on the basis of a comprehensive assessment of the efficiency of the innovation activity of the industrial enterprise, which allows conducting a systematic, comprehensive, operational analysis of the industrial-economic, innovation activity of the enterprise, to find out the need for the development of an economic mechanism, to formulate recommendations for its use. It was established that in the process of the methodological approach's development the sequence of stages was formed that should be followed when using this approach, a comprehensive assessment of the efficiency of innovation activity and the development of the economic mechanism was implemented. The necessity of calculating the indicators of the developed approach in order to consider the specifics of the activity of the mechanical engineering enterprises, to determine the level of financial and economic activity, the feasibility of forming an economic mechanism and the possibility of using this approach not only in the theoretical but also in practical aspects. It is determined that the methodological approach is aimed at establishing the activity of the enterprises of mechanical engineering by using the economic mechanism and forming the possibilities of enterprises for planning of development for the future.