The invention relates to high-speed-stamping cold work die steel and a preparation method thereof. The high-speed-stamping cold work die steel is characterized by primarily comprising, by mass, 0.85%-0.95% of C, 0.80%-1.20% of Si, 0.30%-0.60% of Mn, 0.025% or less of P, 0.015% or less of S, 7.90%-8.40% of Cr, 1.40%-1.70% of Mo, 1.90%-2.20% of W, 2.20%-2.50% of V, 0.90%-1.20% of Al, 0.20% or less of Cu, 0.25% or less of Ni, and the balance Fe. By adding the alloy element, namely Al, the hardness, red hardness and the surface hardness and heat stability after nitriding of the steel are further improved; through addition of Mo, the hardenability, heat resistance, temper embrittlement resistance and temper softening resistance of the steel can be improved; and the high-speed-stamping cold work die steel has the remarkable beneficial effects of having high hardness, heat hardness and heat stability, meeting the development demand of modern industry, reducing consumption and increasing social benefits.