Steel arch frame replaced such construction methods as floor bracket or segment cantilever assembly and it was applied to arch circle cast-in-place across deep water canyons in mountainous areas，which had certain advantages and was worth promoting and applying.By introducing the key construction technologies of Sanchahe Bridge，including steel arch frame cantilever fastener method assembly，arch water tank method precompression，and main arch ring layered pouring，the common problems in the construction process of crossing the deep water canyon were solved effectively.Based on Midas Civil overall modeling of finite elements，the key construction technologies adopted by the bridge were numerically simulated and analyzed，and the successful construction of the bridge was guided and monitored，aiming to provide a reference for similar engineering construction and force calculation and analysis.