To explore the antiviral effects of the extract from Sargassum fusiforme in vitro.Methods:The antiviral effects of the extract from Sargassum fusiforme for 7 kinds of virus that include respiratory syncytial virus (RSV), herpes simplex virus type 1 (HSV-1) and enterovirus 71 (EV71), coxsackievirus A16, coxsackievirus B2, coxsackievirus B3, coxsackievirus B5 (CVA16, CVB2, CVB3, CVB5) were analyzed.The cell survival rate was observed under the microscope.Results:The extracts of Sargassum fusiforme have good inhibitory effect on these 7 kinds of virus, which was greater than broad-spectrum antiviral agent ribavirin.Especially for EV71, the inhibitory effect was significant with high index of inhibiting virus.Conclusion:The extracts of Sargassum fusiforme have good inhibitory effect on these 7 kinds of virus, laying foundation for further study on broad-spectrum antiviral effects of the extract from Sargassum fusiforme.