The bacterial infection of bone implants is a vital factor leading to implant failure. Superhydrophobic surface with low adhesion can effectively enhance corrosion resistance and antibacterial adhesion properties of magnesium alloy. Herein, the superhydrophobic composite coating of hydroxyapatite (HA)/stearic acid was successfully prepared on magnesium alloy (AZ31B) using hydrothermal method and followed modification of stearic acid. The wettability, corrosion resistance and antibacterial adhesion capacity of the composite coating were studied. The composite coatings confer excellent superhydrophobicity with a contact angle about 152.52 degrees and a sliding angle about 2 degrees, and showed good long-term superhydrophobic stability in air. Meanwhile, during immersion in simulated body fluid (SBF), the superhydrophobic composite coating was converted to hydrophilicity in a short time and exposed the micro-/nano-scale structure surface of HA, which could induce the fast deposition of the mineralized apatite layer. The characteristics endowed the composite coating with the short-term antibacterial adhesion property and long-term corrosion resistance in SBF, which will afford a surface modification strategy for the application of magnesium alloy implants in orthopedics and dentistry.