Malaria is a disease caused by Plasmodium spp normally transmitted by mosquito Anopheles spp. This disease became known globally and has attracted attention from national and international because it can cause death, especially for infants, toddlers and pregnant mother. However, an endemic plant Papua that is used as anti-malaria, is Archangelsia flava.Merr. This study was aimed to determine the activity value of anti-plasmodium alkaloids fraction using methanol extract of bark Archangelsia flava.Merr against Plasmodium falcifanrum during 48 hours of in vitro incubation. Alkaloid fraction obtained from the separation of the methanol extract using liquid-liquid extraction with various solvents of acidic and alkaline. Plasmodium culture was applied chandel jar method meanwhile anti-plasmodium activity test was conducted using in vitro. The activity of anti-plasmodium stated through Inhibition Concentration (IC50) value which known to inhibit 50% growth of Plasmodium. The results showed that value of IC50 throughout 48 hours of culturing process was 0.051 μg /mL. Therefore, it is concluded that the alkaloids fraction of Archangelsia flava Merr bark contained anti-plasmodium activity and has performed excellently during 48 hours of culturing process.