Magnesium borate whisker reinforced aluminum alloy 2024 (AA2024) composite was fabricated by squeeze casting method, after was CuO coating of the whisker. The interfacial reaction in the composite was investigated. To change the interfacial reaction degree, the solution treatment for different time was carried out. The results show that the interfacial reaction degree increases with solution time increasing. The maximum ultimate tensile strength can be obtained when the solution time is suitable.