The invention discloses a rhenium-free nickel-based single crystal superalloy and a preparation method thereof. The composition of the rhenium-free nickel-based single crystal superalloy of the present invention is represented by mass percentage as 7.25-7.75% of Cr, 4.8-5.2% of Co, 1.8-2.2% of Mo, 7.8-8.2% of W, and 6.3-6.7% of Ta , 6.0-6.2% Al, 0.12-0.18% Hf, 0.04-0.06% C, 0.003-0.005% B, 0.010-0.030% Y, and the rest is Ni. The preparation of the above-mentioned rhenium-free nickel-based single crystal superalloy comprises the following steps: using a vacuum induction furnace to melt the master alloy, and preparing a cast rod of the master alloy by gravity casting; using the seed crystal method to pass the Bridgeman directional solidification technology at a temperature gradient of 150-250K / cm , the single crystal test bar was prepared at a pulling rate of 5-100 μm / s; the single crystal superalloy was solid solution treated in the range of 1295-1305 °C for 2-4 hours, followed by air cooling, and then in the range of 1090-1310 °C 2-4 hours of high-temperature aging treatment within 2-4 hours, followed by air cooling; then 16-24 hours of low-temperature aging treatment in the range of 850-890 ° C, followed by air cooling.