This work focused on enhancing the comprehensive performance of a novel hollow glass microsphere reinforced Mg-15Al-5Zn-1.5Cu composites through heat treatment. Optical microscopy and scanning electron microscopy were employed to characterize the microstructure evolution. Using a combination of compression tests, immersion tests and electrochemical tests, the effects of heat treatment on mechanical properties, and degradation behavior, as well as the influence mechanisms were comprehensively examined. The results demonstrated that variations in the quantity and shape of the Mg₁₇Al₁₂ and Al₂CuMg phases were primarily responsible for changes in the mechanical properties and degradation rate of the composites. After solution treatment at 420 °C for 20 h and aging at 200 °C for 24 h, the composites exhibited a more uniform microstructure and distribution of secondary phases, and the segregation and residual stress were also eliminated. This endowed the composites with a desirable overall performance: ultimate compressive strength of 435 MPa, hardness of HB 124, fracture strain of 8.3%, and degradation rate of 151 mg/(cm²·d) at room temperature, which made them more beneficial to the applications involving degradable downhole tools.