The microscopic and macroscopic microstructural characteristics as well as the high-temperature mechanical properties of ZTA15 cast titanium alloys were systematically investigated under various mass ratios of alloying elements. Furthermore, the influence mechanisms of different casting processes on the microstructure and mechanical performance of the alloy were explored. Single-cast test samples were fabricated through melting and casting procedures. Following hot isostatic pressing and annealing, the chemical composition and mechanical properties of the samples were comprehensively  analysed to determine the optimal alloying element ratio range that results in superior overall performance. Additionally, a comparative analysis was conducted on samples produced via two distinct casting techniques, investment precision casting and graphite mold casting, to elucidate the specific effects of the casting process on high-temperature mechanical properties. On the basis of the experimental findings, the optimal mass ratio range of alloying elements and the corresponding casting process for ZTA15 cast titanium alloy under high-temperature service conditions of 400 ℃ are identified.