Cu_0.7Mn_0.3Al_2.5 ternary solid solution spinel catalysts were prepared by ball milling method using copper nitrate as the copper source, proposed thin alumina as the aluminium source, citric acid as the additive, and manganese acetate as the third component to partially replace copper. With the help of characterisation techniques such as XRD, BET, H₂?TPR and XPS, the crystalline phase structure, weaving properties, reducing properties and surface cation states and distributions of Cu_0.7Mn_0.3Al_2.5 were investigated. The catalytic performance of Cu_0.7Mn_0.3Al_2.5 in methanol steam reforming (MSR) for hydrogen production with a sustained release feature was scrutinized, and a comparison was made with CuAl_2.5 binary spinel and Cu_0.7Zn_0.3Al_2.5 ternary spinel catalysts. The results showed that compared with CuAl_2.5 and Cu_0.7Zn_0.3Al_2.5, the Cu_0.7Mn_0.3Al_2.5 exhibited the maximum contraction of the unit cell, resulting in a smaller unit cell constant. The catalyst had smaller crystalline size and higher specific surface area. The catalyst showed an aluminium?rich state, but with a higher percentage of Cu in the surface spinel phase, which made the reduction under H₂ atmosphere more difficult, and exhibited a better slow?release catalytic performance in MSR hydrogen production. Under the conditions of a reaction temperature of 265 °C, n（H₂O）/n（CH₃OH） =2, and mass flow rate of 2.25 h^-1, a stable conversion rate of 84% was achieved for 40 hours. The study provided valuable data reference for the development of efficient copper?based sustained?release catalysts.