N-doped TiO2 (N-TiO2) photocatalyst was prepared by the sol-gel method, using butyl titanate and urea as raw materials, and then loaded onto diatomite to prepare a composite photocatalyst. Bleached sulfate softwood pulp fiber was dissolved and mixed with the composite photocatalyst and then regenerated to prepare composite fillers for the manufacture of visible light-responsive photocatalytic paper suitable for the removal of toxic formaldehyde gas. Photocatalytic paper containing 20% composite filler with a ratio of 4/6 N-TiO2 (60% N-doping)/diatomite had good photocatalytic activity, with 50.1% formaldehyde degraded after 10 h under visible light irradiation. This photocatalytic paper also had good physical properties, with a paper density of 0.36 g cm−3, a burst index of 3.0 kPa·m2 g−1 and a tensile index of 43.33 Nm g−1, indicating that it has good prospects for removal of indoor air pollutants. [ABSTRACT FROM AUTHOR]