A novel β-1，3-glucanase from Arca inflata was purified using chromatography methods. It was determined as a glycoprotein comprising 23.65% carbohydrate content with O-linked glycan and showed specific activity of 90.01?±?1.2?U/mg against laminarin. The optimal pH and temperature for the activity of the glucanase were 6.0 and 40?°C， respectively. The affinity parameter of the glucanase using laminarin was determined as K?=?13.09?μM. The activity of the glucanase was 27?±?2.6% enhanced by 2-mM Mn ions and inhibited by 40-50% using 2-mM Zn， Cu， or Ba ions. The glucanase showed an endo-type cleavage mode and hydrolyzed laminarin into glucoses， disaccharides， trioligosaccharides， and tetraoligosaccharides. Otherwise， the glucanase exhibited immune-enhancing effects via significantly increasing the phagocytic activity of macrophages and inducing the release of nitric oxide， tumor necrosis factor α， and interleukin-6 in RAW264.7 cells. It might be used as a bifunctional additive for the food industry.