A belt structure includes a first housing, a second housing, a third housing and a belt. The two ends of the belt are respectively connected to the first housing and the third housing, which can be buckled together quickly. The second housing and the first housing are connected, so that a mechanism for fine tuning the belt can be formed through the gear, the driving element and the resisting element in the first and the second housing, thereby a belt structure with fast buckling capability and fine tuning function can be achieved.