Small and medium-sized Enterprises are the result of new ideas for production that are considered as components of job creation and wealth. The development of these enterprises in the downstream petrochemical industry is one of the most important strategies to create added value for petrochemical basic products, especially in countries with oil and gas resources. High job creation compared to the amount of investment, the existence of appropriate domestic demand, the attractiveness of export markets and government support programs to strengthen domestic production, are the advantages of developing these businesses. In this research with a qualitative research approach, first by studying the library and interviewing experts, the most important obstacles to the development of small and medium Enterprises in the rubber and plastic industry of Kermanshah province have been identified and using the DIMATEL technique, the effective and impressive organized themes were examined. Then, in order to rank these themes, the network analysis process technique was used. Lack of industrial development, financing barriers, weak business culture and administrative and regulatory barriers were among the effective(causal) factors and production barriers and sales and marketing issues were included in the category of influential (impressive) factors. In the ranking, financing barriers, production barriers and lack of industrial development in the province have the largest share in the research topic.