The invention discloses a method for preparing a noble-metal-supported p-NiO / n-NiFe2O4 composite semiconductor photocatalyst. The method comprises the following steps of: 1, sequentially performing microwave reaction on nickel salt, iron salt, citric acid, alkali and deionized water which are taken as raw materials, performing ultrasonic dispersion, heating and reacting, washing, performing ultrasonic dispersion, filtering, drying, roasting and grinding to obtain NiFe2O4 solid powder; 2, sequentially reacting the NiFe2O4 solid powder, nickel salt, alkali and deionized water which are taken asraw materials, performing ultrasonic dispersion, dehydrating under reduced pressure, performing heat treatment, washing, performing ultrasonic dispersion, filtering, drying, roasting and grinding to obtain p-NiO / n-NiFe2O4 solid powder; and 3, sequentially stirring the p-NiO / n-NiFe2O4 solid powder, a noble metal compound, ethanol and deionized water which are taken as raw materials and dissolving,performing ultrasonic dispersion, performing photochemical deposition reaction, removing a solvent under reduced pressure, performing heat treatment, washing, filtering, drying, roasting and grindingto obtain the noble-metal-supported p-NiO / n-NiFe2O4 composite semiconductor photocatalyst.