The study investigated the influence factors of the ultra-high performance seawater sea-sand con? crete (UHPSSC), and optimized its overall performance. The orthogonal experiments were first conducted to study the effects of water binder ratio, sand binder ratio, silica fume content and fly ash content on the mechanical properties and fluidity of UHPSSC, and the optimal mix design is obtained. Then, based on the optimal mix proportion from the orthogonal test, the effects of volume fraction and short-cut fiber type on the mechanical properties of UHPSSC were studied, including polypropylene fiber, polyvinyl alcohol fiber, basalt fiber, alkali resistant glass fiber, ultra-high molecular weight polyethylene fiber and steel fiber. The results show that the most influential factors on the fluidity, the flexural strength and the compressive strength are water binder ratio, water binder ratio and fly ash content. Based on the comprehensive evaluation of mechanical performance and flowability, the optimized mix design is the dosage of cement, silica fume, fly ash, water and sea sand per cubic meter of concrete is 491 kg，140 kg，70 kg，112 kg and 631 kg, respectively. Meanwhile, the enhancing effect of steel fiber on the mechanical performance of UHPSSC is most ob? vious.