Abstract:The systemic resistance and protection effect of laminarin against Tobacco mosaic virus (TMV) was determined in this paper. The inhibition effects of four antiviral agents lentinan 0.5% AS, 0.5 mg/mL laminarin AS, 0.1 mg/mL moroxydine+copper acetate WP, oligosaccharins 6.25 mg/L AS against TMV were investigated using the ELISA assay. The dynamic activities of superoxide dismutase (SOD), peroxidase (POD), phenylanine ammonialyase (PAL) were measured, and the contents of chlorophyll were tested after application of laminarin. The results showed that in vitro, laminarin and oligosaccharins provided relatively good protective effects against TMV, with inhibition rate 42.42%, 44.96%, respectively, while their therapeutic effects were not obvious, with inhibition rate 38.93%, 40.13%. Activities of PAL, SOD, POD in tobacco leaves were increased after spraying laminarin solution and the contents of chlorophyll were prevented from decreasing. In conclusion, laminarin had the ability to induce the systemic resistance on tobacco against TMV infection, and could protect the host from virus infecting.