The invention discloses C20 concrete for preliminary bracing of tunnel steel shotcrete and a die-cast shotcrete technology. The concrete is prepared from cement, gravel, sand, an additive and water. The technology comprises the steps of firstly performing anchor rod hole construction on a tunnel wall according to designed intervals and performing anchor rod pouring construction in holes within hole depths; then performing outer layer reinforcing mesh laying construction, wherein a reinforcing mesh is tightly attached to a rock surface and fixed to anchor rods; then installing a steel arch in a tunnel; installing an inner layer reinforcing mesh between the steel arch, wherein the two sides of the inner layer reinforcing mesh are fixed to the steel arch; finally pressing a detachable formwork on the arch from the bottoms of the two sides of the steel arch, installing and fixing, forming a concrete cabin, spraying concrete into the concrete cabin in a mode perpendicular to the rock surface, disassembling the formwork after concrete solidifies, circularly pressing, installing and fixing the formwork to parts where concrete is not sprayed of the steel arch and performing continuous spray operation. The concrete has the characteristics of low rebound rate and moderate slump degree.