The invention discloses a method of processing Antrodia cinnamomea for producing a processed sample of Antrodia cinnamomea, which easily releases antcin K in a following extraction process. The method includes the steps of: soaking a raw sample of Antrodia cinnamomea with a processing reagent comprising 25-83.3 wt % of rice vinegar and 16.7-75 wt % of yellow wine at 22-28° C. for 22-26 hours; and steaming the soaked product at 1-3 kg/cm2, 110-150° C. for 10-50 minutes.