The invention relates to an airspace defense method and an air floating mine thereof. In the method, a transparent hydrogen balloon or helium balloon matched with a high-energy miniature bomb is arranged in a fortified airspace. The bomb is matched with a self-destroying device of clock control or controller control for spontaneous explosion mine removal, and is matched with an identification friend or foe system to prevent bombing error. The air floating mine comprises the transparent hydrogen balloon or helium balloon matched with the high-energy miniature bomb, and the balloon is matched with a height maintaining system. The method has the advantages of low cost and easy defense organization, can effectively block or inhibit the air power of the enemy, and is particularly suitable for a side with weak air power for defending against the invasion of an enemy with strong air power. The floating mines can be set at high density in a large scale by rockets or missiles or planes, and continuously float in a certain airspace for attacking an air target of the enemy colliding or approaching the floating mines, thus achieving the purposes of forcibly blocking or inhibiting the air power of the enemy by low cost and safeguarding the mastery of the air.