Enterprise green development is a new development path. To effectively track M&A performance of manufacturing enterprises, this paper is based on M&A of the iron and steel enterprises, building a three-layer index system including M&A economic performance, environmental performance and social performance index, and using cluster analysis to evaluate the change of the M&A performance. The research results show that in the context of green development, there are two extremes in the post-merger performance of enterprises. Some enterprises have obtained higher economic performance and social performance through M&As. The other enterprises have obtained higher environmental performance through M&As. However, there are no enterprises obtained with higher economic performance, environmental performance and social performance at the same time. Therefore, it is a long way to balance the development of the economic prosperity, environmental protection and social welfare in future. The innovation of this paper is based on the Theory of Triple Bottom Line building a three-layer M&A performance index system, then using the hierarchical cluster analysis method to analyse M&A performances of manufacturing enterprises, and the result is more targeted.