In this work, non-noble metal cobalt hydroxide nanoparticles [Co(OH)₂ NPs] implanted uniformly on graphitic carbon nitride (g-C₃N₄) as a co-catalyst for hydrogen evolution reaction (HER) by in-situ chemical deposition method were reported. After co-sensitized by Eosin Y (EY) and Rose Bengal (RB) dyes, this photocatalyst exhibited a comparatively low onset potential (0.26 V) for HER and high photocatalytic HER activity under visible light irradiation. The g-C₃N₄ not only provided a large area and nanoporous structure for the confined growth of Co(OH)₂ NPs, but also greatly facilitated EY and RB (ER) molecules assembling on its surface, which promoted the charge transfer from dye to co-catalyst. The PL spectra and lifetime test showed the strong interaction between Co(OH)₂ NPs and g-C₃N₄ could enhance the transferr rate of the photogenerated electron to reduce the carries recombination. About 431.9 μmol of hydrogen generated over ER co-sensitized Co(OH)₂/C₃N₄ in 3 h. The apparent quantum efficiencies (AQE) of 29.6 and 27.3% were achieved at 520 nm and 550 nm over Co(OH)₂/C₃N₄, respectively. In addition, this co-sensitized photocatalyst showed satisfied stability for HER, no remarkable decay of activity was observed in 900 min reaction. These results imply that Co(OH)₂ is a stable and efficient cheaper co-catalyst for photo-HER.