Based on the theory of multimodal discourse analysis, this study analyzes the synergistic effects of textual, visual, and other semiotic resources in Alibaba’s official ESG reports, revealing how these resources construct environmental narratives and empower corporate image through semiotic practices. The research, conducted from the dimensions of representational meaning, interactive meaning, compositional meaning, and modal synergy, deciphers how the semiotic system deeply integrates ecological concepts. The findings indicate a high degree of text-image synergy during the 2022–2024 period, effectively presenting themes such as “Repairing the Green Planet,” “Digital Empowerment for Carbon Reduction,” and “Clean Energy and Circular Economy.” However, the visual presentation in the 2025 report is relatively concentrated on flowcharts and data graphs, showing insufficient multidimensional representation of environmental modules and public engagement, with an overall weakening of text-image synergy. This study enriches the application of multimodal analysis in the field of environmental narrative research. Its theoretical and practical value lies in revealing the strategic role of semiotic synergy in building a sustainable brand and providing a communication pathway reference for promoting public environmental awareness and sustainable consumption behaviors.