Nanowire photocatalyst Bi20TiO32 was modified by carbon quantum dots (CQDs). CQDs/Bi20TiO32 showed much higher photocatalytic activity than pure Bi20TiO32. The introduction of CQDs accelerated separation of photo-induced charge carriers. O2− and h+ were the dominant active species to decompose isoproturon. PAN-CQDs/Bi20TiO32 nanofiber mats exhibited good recyclability and high stability.