The load deflection curves of emulsified asphalt cement mortar were tested by three point bending test at different temperatures, and the fracture energy was obtained by integrating the area under the load deflection curve. The effect of temperature on the toughness of emulsified asphalt cement mortar was revealed. The microstructure of emulsified asphalt cement mortar was observed by scanning electron microscopy（SEM）. The results indicate that, with the increase of temperature from -40℃ to 80℃, the fracture modes of emulsified asphalt cement mortar in bending transform from brittle fracture to ductile fracture, finally to flexible fracture. When the ratio（by mass） of asphalt to cement is 030, the toughness of emulsified asphalt cement mortar shows little change as the temperature variation. When the ratio of asphalt to cement ranges from 045 to 090, the toughness of emulsified asphalt cement mortar increases at first and then decreases gradually with the increase of the temperature, and reaches the maximum value at about -10℃. It is concluded that the higher the ratio of asphalt to cement, the greater the temperature sensitivity of the toughness. When the ratio of asphalt to cement increases, the continuous film of asphalt in the emulsified asphalt cement mortar appear, and with the ratio of asphalt to cement continued increasing, the thickness of the asphalt film raises, which leads to the increase of the temperature sensitivity of the toughness.