The invention relates to a sea-air amphibious unmanned platform and an operating method thereof. The sea-air amphibious unmanned platform comprises a flat platform main body, a power source power system, a buoyancy adjusting system, a control system and a wing-shaped adjusting system, foldable subsidiary wings are symmetrically connected to the two sides of the platform main body, the tail end isconnected with an empennage mechanism, an empennage comprises a horizontal foldable empennage and a vertical empennage rudder, the buoyancy adjusting system comprises a ballast tank arranged on the platform main body, an air inlet and outlet hole, a water inlet and outlet hole are vertically formed in the ballast tank separately, the ballast tank is connected with a submerged pump, a propeller capable of jetting to the rear lower portion of the platform main body is arranged at the front end of the platform main body, and both the power source power system and the control system are electrically connected with the submerged pump, the win-shaped adjusting system and the propeller. The sea-air amphibious unmanned platform can integrate the functions of air flying, water surface sailing, underwater sailing/ gliding, during water surface sailing taking off, an air cushion can be formed under the unmanned platform, thus the taking-off weight and load are effectively increased, and meanwhile, power is saved.