The present disclosure provides various cyanobacterial extracts exhibiting antiviral activity to a wide spectrum of viruses, such as enterovirus (EV), respiratory syncytial virus (RSV), Ebola virus, porcine epidemic diarrhea virus (PEDV), and porcine reproductive and respiratory syndrome virus (PRRSV). The cyanobacterial extract is prepared from biomass ofA. maxima(orSpirulina maxima). Also disclosed herein are process for preparing the cyanobacterial extract and uses of the cyanobacterial extract.本揭示內容提供多種藍綠藻萃取物,其對多種廣泛的病毒能夠展現抗病毒活性,譬如腸病毒、呼吸道融合細胞病毒、人類疱疹病毒、伊波拉病毒、豬流行性下痢病毒及豬生殖與呼吸綜合症病毒。所述的藍綠藻萃取物係由極大節螺藻(或稱極大螺旋藻)的生物質所製得。此處亦揭示用以製備所述藍綠藻萃取物的方法及所述藍綠藻萃取物的用途。