Rational design and facet-engineering of nanocrystal is an effective strategy to optimize the catalytic performance of abundant and economic semiconductor-based photocatalysts. In this study, we demonstrate a novel ternary Cu₂MoS₄ nanotube with the {010} facet exposed, synthesized via a hydrothermal method. Compared with two-dimensional Cu₂MoS₄ nanosheet with the {001} facet exposed, this one-dimensional nanotube exhibits highly enhanced performance of photodegradation and water splitting. Both theoretical calculations and experimental results suggest that the conduction band minimum (CBM) of the {010} facet crystal shows lower potential than that of the {001} facet. In particular, the up-shifted CBM in Cu₂MoS₄ nanotube is significantly beneficial for the absorption of dye molecules and reduction of H⁺ to H₂. These results may open a new route for realizing high-efficiency photocatalysts based on Cu₂MX₄ by facet engineering.