Although the traditional metal oxide catalyst has high activity and strong degradation ability, the forbidden bandgap is generally larger, and the utilization rate of sunlight is much low. Moreover, the high internal resistance inhibits carrier transfer, so the photoelectrochemical performance needs to be improved. Selenides with narrow bandgap and low internal resistance are promising candidates for photocatalysts. A new type of 1D/2D selenide heterojunction was constructed by compositing MoSe 2 and FeSe 2 , two kinds of narrow bandgap metal selenides. In this 1D/2D heterojunction, MoSe 2 presents a three-dimensional network structure, which can effectively collect and transport optical carriers, and it is an ideal heterostructure as a substrate loaded with 1D FeSe 2 nanorods. Moreover, this heterojunction has good light absorption characteristics and can achieve full spectrum absorption of ultraviolet and visible light. This FeSe 2 /MoSe 2 composite has photocatalytic performance more than 3.4 times that of MoSe 2 , and its photoelectrochemical performance is more than 2 times. The experimental results show that FeSe 2 / MoSe 2 is an ideal composite system with great potential in photocatalysis.