Objective: This study provided basic data for the investigation of polysaccharides in coffee and the development of natural active polysaccharides. Methods: The water extraction method and antioxidant activity of green coffee beans polysaccharide (GBP) from Yunnan province. Response surface method was used to optimize the extraction process of polysaccharide from coffee bean. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) were used to identify and characterize the structure of polysaccharide from coffee bean. DPPH, ABTS free radical scavenging assay and FRAP assay were used to evaluate the antioxidant capacity of coffee bean polysaccharide in vitro. Results: The optimal extraction conditions were as follows: extracting at 59 ℃ for 45 min, liquid-solid ratio (V_W∶m) 21∶1 (mL/g), concentrated volume 1/8 and ethanol volume fraction 75%. Under the control of these conditions, the yield of polysaccharides from coffee beans reached 9.56%. The results of FT-IR and electron microscopy showed that the polysaccharide of coffee bean had irregular pore structure. The DPPH scavenging capacity and ABTS radical scavenging capacity of coffee bean polysaccharide was 2.32 mg/mL (IC₅₀) and 0.011 mmol Trolox/g GBP, respectively. The iron reducing capacity of coffee bean polysaccharide was 0.95 mmol Fe²⁺/g GBP. Conclusion: Polysaccharide derived from green coffee beans is a kind of polysaccharide with irregular pores and antioxidant activity, which is valuable for further research and development.