The invention discloses high-hot-strength spray-formed hot work die steel and a preparation method thereof, belonging to the technical field of hot work die steel. The die steel comprises the following components of 0.3-0.5 of C, 3.0-5.0 of Cr, 1.5-3.5 of Mo, 0.4-1.0 of W, 0.3-0.8 of Si, 0.3-0.5 of Mn, 0.8-1.5 of V, 0.03-0.10 of Nb, less than or equal to 0.03 of S, less than or equal to 0.03 of P and the balance of Fe. The preparation method comprises the process routes of spray forming, hot forging and heat treatment; different comprehensive mechanical properties are obtained by adjusting the quenching and tempering temperatures in a way of controlling process parameters and hot forging temperature in the spray forming process, so that the requirements of different working conditions are met. The compatibility of alloy elements is reasonably optimized according to the characteristic of a spray forming process and the special requirement of the hot work die steel for high-temperature performance, so that the high-hot-strength spray-formed hot work die steel has favorable high-temperature performance, good heat stability and tempering resistance, relatively high impact toughness and excellent comprehensive performance, and the service life of the hot work die steel is greatly prolonged.