The influence and mechanism of biochar on the compressive strength and carbon sequestration of carbonation-cured cement mortar were studied. The results show that addition of biochar can effectively promote early hydration reaction of cement， as well as improve compressive strength and pore structure of carbonation-cured cement mortar. This improvement effect becomes more obvious with the prolongation of carbonation duration. Besides， incorporation of biochar decreases carbon sequestration in carbonation curing， while the total carbon sequestration by biochar and carbonation curing increases significantly by considering both biochar and cement paste.