The influence of mineral admixtures on mortar brittleness is analysed in this paper. Test results show that the mortar brittleness increases with the increasing of compressive strength and the passage of age. When the content of binding materials rises, the compressive strength also increases, but the brittleness decreases at the same time. The more the content of fly ash is, the more the brittleness falls. Silica fume added can not only enhance compressive strength but also reduce brittleness of the mortar. MgO added can cut down the brittleness, but can reduce the compressive strength a little at the same time, especially for early compressive strength.