The invention relates to a preparation method for a photocatalyst and aims at providing a preparation method for a (101)-surface nanoFe-TiO2 high-efficiency nitrogen-fixing photocatalyst. The preparation method comprises the following steps of: preparing a compound containing titanium and a concentrated alkaline solution into a mixed suspension, completely dissolving the mixed suspension and then carrying out constant-temperature hydro-thermal reaction; washing with a hydrochloride solution and deionized water and carrying out suction filtration to obtain a white precipitation, namely hydrogen phthalate; drying and grinding the hydrogen phthalate to obtain white powder hydrogen phthalate; adding the hydrogen phthalate into deionized water for fully mixing and adjusting the pH value with a dilute acid solution; doping an iron source, adding the hydrochloride solution and the deionized water and stirring to be dissolved; slowly dropping the mixture into the suspension while stirring; and continuously stirring at room temperature, adding the deionized water and urea and carrying out stirring, hydro-thermal reaction, suction filtration, washing, drying, calcining and grinding to obtain the (101)-surface nanoFe-TiO2 high-efficiency nitrogen-fixing photocatalyst. The preparation method disclosed by the invention has the advantages of simple raw material, wide source, simple and convenient preparation process, easily-controlled conditions, adjustable process parameters, low energy consumption, low cost and capability of realizing mass preparation in a short time. The photocatalyst is uniform in doping, smooth in surface and favorable in photocatalytic activity.