Inorganic-organic hybrid nanomaterials, with excellent chemical and physical properties and technology applications, have attracted much attention in many fields. In the photocatalytic field, it is still a problem to find a stable, adjustable morphology and band gap and effective photocatalyst in utilizing solar energy conversion to hydrogen (H2) to solve the energy crisis. Herein, with the assistance of diethylenetriamine (DETA), the novel inorganic-organic CdSe-DETA hybrids with different morphology and adjustable band gap have been synthesised via simple microwave hydrothermal method. The morphological transformation mechanism involves the consumption of organic components controlled by the mixed precursor and subsequent self-assembly of residual inorganic components (CdSe). Under the visible light irradiation (λ > 420 nm), CdSe-18DETA nanobelt, showed the best photocatalytic H2 production activity (5.75 mmol·g-1·h-1), which is 3.03 times greater than that of pure CdSe (1.90 mmol·g-1·h-1). Moreover, after four cycles, the photocatalytic H2 production activity can still remain 91.27% of initial value, which indicates its good photocatalytic stability. Our results provide a promising approach for designing visible-light photocatalysts with efficient electron-hole separation and adjustable morphology and band gap.