The invention discloses an S-1 full-silicon molecular sieve and a preparation method thereof as well as application of the S-1 full-silicon molecular sieve in caprolactam preparation. The S-1 full-silicon molecular sieve is prepared by the method comprising the following steps: (1) synthesizing a tetrapropylammonium hydroxide template agent; and (2) synthesizing a molecular sieve: carrying out a reaction on tetrapropylammonium hydroxide liquor and tetraethoxysilane and ethanol, filtering, washing with deionized water, drying reaction liquid, roasting, so as to obtain molecular sieve raw powder; adding silica sol, polyethylene glycol 2000, and stronger ammonia water, sesbania powder and activated carbon powder in the molecular sieve raw powder, kneading in a kneader, then carrying out extrusion; roasting, immersing the roasted product in a NH3-NH3NO3 mixing solution and a hydrofluoric acid solution respectively, washing with deionized water, drying, roasting again so as to obtain the S-1 full-silicon molecular sieve. In the invention, the template agent is cheap; the conversion rate of the cyclohexanone and selectivity of the caprolactam are extremely high; a catalyst can be easily and fast regenerated; and the use of concentrated sulphuric acid is avoided, thus the S-1 full-silicon molecular sieve and the preparation method thereof are environment-friendly.