With a purpose to determine the connection between mechanical property and fracture habits of UHSC and examine its influencing elements, a collection of UHSC with totally different combine proportion have been ready. The mechanical properties (together with compressive energy, flexural energy, and splitting tensile energy) had been examined on a hydraulic servo common testing machine. Three-point bend loading methodology was used to measure the fracture parameters (together with fracture toughness and attribute size) and a crack was prefabricated within the pattern. The outcomes present that the energy of UHSC decreases with w/b ratio and the utmost compressive energy and flexural energy can attain 132 MPa and 21.5 MPa, respectively. UHSC shows important brittle fracture habits and its brittleness will increase with energy. The principle cause is that the micro-defects of UHSC are diminished and the homogeneity of the entire cement matrix is enhanced, thus the crack initiation energy is improved however crack resistance skill is impaired. Excessive temperature curing will increase the energy in addition to brittleness of UHSC. Including fly ash will enhance its attribute size however scale back the facture toughness. Our work could present steering for decreasing the brittleness of ultra-high energy concrete.