Abstract: Activated by alkaline activator, polyethylene (PE) fiber reinforced high ductile alkali-activated slag composites were prepared using slag as the main raw material and fly ash as auxiliary material. The tensile and compressive properties of the composites under different curing ages (1 day, 3 days, 7 days, 28 days, 56 days and 120 days) were studied through uniaxial tensile and compressive tests, and the cracks were characterized by a digital image correlation technology (DIC). The results show that the alkali-activated slag owns a good high ductility and early strength. The strength value at 7 days can reach more than 84% of the ultimate strengths (the ultimate tensile and compressive strengths are 5.05 MPa and 91.24 MPa, respectively), 5.74% for the tensile strain, and the multi-cracking is basically saturated. After 28 days, the tensile and compressive properties become stable (tensile and compressive strengths and tensile strain keep around 6 MPa, 100 MPa and 6%, respectively). DIC analysis cloud maps visually describe the formation and propagation of cracks, which can be applied to predict reliably the direction and location of cracks to a certain extent.