The invention discloses low-cost, ultra-pure, high-strength and high-toughness low-carbon stainless bearing steel and a preparation method thereof. The bearing steel is prepared from the components including 0.13%-0.30% of C, 0.05%-0.2% of Si, 0.02%-0.1% of Mn, 13.6%-16.80% of Cr, 2.1%-4.0% of Ni, 12.5%-17% of Co, 5%-6% of Mo, 0.7%-2.5% of W, 0.7%-1.2% of Nb + V, less than or equal to 0.025% of P+S+Ti, less than or equal to 0.0012% of Ti, less than or equal to 0.0007% of O, less than or equal to 0.0015% of N+H, less than or equal to 0.0014% of N, 0.05%-0.08% of Al, 0.005%-0.015% of Ce, 0.005%-0.02% of La, 0.01%-0.03% of Y, and the other element of Fe. The preparation process route comprises the steps of molten steel primary smelting, AOD refining, LF refining, IC casting, VIM smelting, ESR electroslag remelting and VAR vacuum consumable remelting. Compared with the prior art, the low-carbon stainless bearing steel is lower in production cost, higher in strength and toughness, longer in fatigue life and extremely low in oxygen and nitrogen impurity content.