Nano-imprint technology is a method of nano-pattern reproduction, has the characteristics of high resolution, high throughput, and low-cost. It can reduce the complexity and cost of the equipment while improving the resolution, which considered a promising industrial production technology. The key to nanoimprinting lies in the mold, and the quality of the mold directly determines the quality of the imprinted graphics. Here, a method for fabricating sub-100 nm concave 2D silicon nano-mold by side etch lift-off is proposed. The effects of different wet etching time and the metal deposition angle on the width of nanochannels were studied. The measurement result of dry etching shows that on the entire 4 inch silicon wafer, the width of the nanochannel varies by 4% and the depth by 2%. The width of the nanochannel between chips varies by 0.7%, and the depth variation is 1%. With this new method, high-precision and large-scale silicon nano-mold can be produced, which has great potential for realizing high-precision and low-cost manufacturing of nano devices.