Electroless copper plating is an important measure of metalizing surface of alumina ceramic substrate. The work aims to further optimize the process of electroless copper plating on alumina ceramic substrate by studying the effects of chemical copper plating bath proportion (especially content of copper ion and formaldehyde in the bath) on microstructure and electrical conductivity of copper coating. After pretreatment of alumina ceramics substrate, copper coating on the substrate was carried out by virtue of electroless copper plating. Phase and morphology of the coating subject to electroless copper plating on alumina substrate were observed with X-ray diffractometer and optical microscope, respectively. The coating thickness and sheet resistance of the coating subject to electroless copper plating on alumina substrate were measured by coating thickness gauge and four-probe tester, respectively. XRD results showed that all coatings subject to electroless copper plating prepared in different proportion exhibited better crystallinity. Moreover, plating bath of lower content of formaldehyde and copper could be used to produce copper coating with fine grains. The deposition rate was high when the content of formaldehyde and copper ion was high, leading to poor compactness and uniformity of copper coating. Meanwhile, the deposition rate was moderate when the content of formaldehyde content was higher and the content of copper ion was lower, leading to better uniformity, compactness and conductivity of the copper coating. When the concentration of formaldehyde and copper sulphate is 0.25 mol/L and 1.2 g/L respectively, copper coating of good uniformity and compactness is prepared by surface active copper plating process without high temperature heat treatment, meeting application requirements of copper-clad laminates.