The suppression of the recombination of electrons and holes (e–h) and the enhancement of the light absorption of semiconductors are two key points toward efficient photocatalytic degradation. Here, we report a few-layer g-C3N4/α-MoO3 nanoneedles (flg-C3N4/α-MoO3 NNs) all-solid-state Z-scheme mechanism photocatalyst synthesized via a typical hydrothermal method in a controlled manner. The recombination of the photo-induced e–h pairs could be effectively restrained by the Z-scheme passageway between the flg-C3N4 and α-MoO3 NNs in the composite, which could also promise a high redox ability to degrade pollutants. And it became possible for the prepared photocatalyst to absorb light in a wide range of wavelengths. The detailed mechanism was studied by electron spin-resonance spectroscopy (ESR). The low-dimensional nanostructure of the two constituents (α-MoO3 NNs with one-dimensional structure and flg-C3N4 with two-dimensional structure) endowed the composite with varieties of excellent physicochemical properties, which facilitated the transfer and diffusion of the photoelectrons and increased the specific surface area and the active sites. The 10 wt% flg-C3N4/α-MoO3 NNs showed the best photocatalytic performance toward RhB degradation, the rate of which was 71.86%, ∼2.6 times higher than that of α-MoO3 NNs.