The effects of mineral admixture on tensile strength and tensile modulus of the mortar specimens and the development of ultimate tensile strength and tensile modulus of elasticity with curing age were studied by digital image correlation technology(DIC). The test results show that with the increase of curing age, the ultimate tensile strength and tensile elastic modulus of mortar specimens all increases linearly. At the same curing age, the hydration degree of cementitious systems is reduced by the incorporation of ground granulated blastfurnace slag（GGBS） and fly ash, so ultimate tensile strength and elastic modulus of the mortar specimens at early age are also reduced.