This study aimed to analyze the antioxidant activity (IC50) of methanol extract using the DPPH method (2, 2-diphenyl-l-picrylhydrazyl) from various post-harvest processing methods (natural, honey, full wash). The first applied SNI 01-2907:2020 on Robusta coffee beans produced from different post-harvest ways. The research method calculates antioxidant activity based on simpilisa preparation, macerate preparation coffee beans, and antioxidant activity testing. The results showed the IC50 value of 119.79 ppm for green coffee beans produced from the Honey processing process had moderate antioxidant activity. The category of moderate antioxidant activity because several mixtures of phenolic compounds did not work optimally to donate hydrogen atoms. The DPPH radical was not maximal in reducing it to stable conditions. The instability is suspected because the raw materials have experienced storage the previous year’s harvest for one year.