The hydration degree and mechanical properties of ultra-high performance concrete (UHPC) specimens with hybrid steel fibers cured in air and hot water (1 d, 60℃ hot water + 2 d air), respectively, were investigated via ignition loss tests and uniaxial tensile and compressive tests. Also, the surface cracking characteristics of tensile specimens were characterized by digital image correlation technique and optical microscopy, and the microstructures were analyzed by scanning electron microscopy. The results show that compared with the results obtained in air curing, hot water curing accelerates the hydration reaction progress of the UHPC matrix, and an increase in temperature mainly contributes to the promotion of hydration reaction, thus improving the initial cracking, tensile and compressive strength of the UHPC specimens in hot water curing. However, the tensile strain capacity changes slightly. In general, the maximum crack width of the specimen decreases, the matrix becomes denser, and the interface bonding between the fibers and the matrix is stronger. The tensile strain of UHPC increases with the increase of fiber content, in which the tensile strains of the specimens with 2.5% (volume fraction) of fibers (a ratio of long fibers to short fibers is 1.25: 1.25 and 1.5: 1.0, respectively) are more than 2 ×10-3, the specimen with 1.5% long fibers and 1.0% short fibers produces more tensile cracks with the width of < 50 μm in hot water curing. The uniaxial tensile strains predicted by DIC are in reasonable agreement with the strains measured.