A preparation method for a surface micro and nano composite structure of a mono-crystalline cell, comprising the following steps: S1, alkali texturing: forming a pyramid textured surface having the reflectivity of 15-17%, and the size of the pyramid being 5-10 μm; S2, primary acid pickling: performing acid pickling by using a HNO3 solution, the concentration of the HNO3 solution being 0.5-1%, the temperature being controlled to be a room temperature, and a time duration of the acid pickling being 60-100 s; S3, silver ion-assisted texturing: forming a nano hole having a diameter of 80-130 nm and a depth of 150-200 nm. According to the method, a conventional mono-crystalline alkali texturing and conventional black silicon silver ion-assisted texturing are combined, and the surface of the mono-crystalline is textured to form a micro-nano composite structure textured surface, which has a low specific surface area while low reflectivity is ensured; surface recombination is reduced, and conversion efficiency of a cell is further improved.