The invention discloses a steel wire rod for a high-strength boron-contained and annealing-free fastening piece and a preparation method thereof. The steel wire rod for the high-strength boron-contained and annealing-free fastening piece comprises the following chemical components in percentage by weight: 0.20-0.24 wt% of C, Si not more than 0.04 wt%, 0.50-0.70 wt% of Mn, 0.25-0.35 wt% of Cr, 0.035-0.055 wt% of Ti, 0.035-0.055 wt% of Als, 0.0045-0.0060 wt% of B, S not more than 0.004 wt%, P not more than 0.012 wt%, O not more than 0.0015 wt%, H not more than 0.00015 wt%, and the balance of Fe and inevitable impurities. The preparation method comprises the steps of molten iron pretreatment desulfurization, molten steel smelting, deoxidation alloying, molten steel LF furnace refining, molten steel VD furnace vacuum refining, molten steel pouring, steel blank heating and controlled rolling and controlled cooling. The steel wire rod for high-strength boron-contained and annealing-free fastening piece is high in cleanness, few in inclusions, excellent in hardenability, proper in strength and hardness and excellent in ductility and toughness and cold heading and upsetting deformation capacity, can directly form a 10.9-grade high-level standard part through cold heading without needing spheroidizing annealing, reduces the processing procedures and the steel consumption, and reduces the production cost.