High-strength concrete is vulnerable to impact damage during service, so it is necessary to prepare high-performance concrete with certain guarantee of strength and impact resistance. In this paper, C100 high-strength concrete was designed with normal-pressure and high-pressure curing process, and its toughness difference law and mechanism were discussed from macroscopic and microscopic levels. The test results show that the difference of compressive strength of concrete under the two curing systems is small, but the difference of splitting tensile strength and flexural strength is big within 28 d. At the same time, the toughness of high-pressure curing concrete is better than that of normal-pressure curing concrete, and its tension-compression ratio, flexural-compression ratio and initial cracking impact energy consumption are 1.37 times, 1.21 times and 1.24 times of that of normal-pressure curing concrete on average. Compared with normal-pressure curing concrete, the internal admixture reaction of high-pressure curing concrete develops more fully with age, and calcium silicate hydrate (C-S-H) is flocculent, which makes it more easily fill the internal weak areas such as pores and cracks. There is no plate-like Ca(OH)2 in the hydration products of high-pressure curing concrete, and C-S-H effectively plays a bridging role. The prepared high-pressure curing concrete has better toughness.