The invention relates to an inner-locking type tube fitting of a connecting rod structure device, and the inner-locking type tube fitting is used as a sealing tube fitting. The inner-locking type tubefitting comprises a blocking plug (1), a locking ring (2), a fastening bolt (3), a connecting rod (4), a connecting handle (5), a driving plate (6), a pin (7), an O-shaped ring (8), a spiral base (9), a fixed bolt (10), a four-way tube fitting (11) and a dowel pin (12). The design idea of the inner-locking type tube fitting refers to discarding a conventional connecting way, and a unique structure is designed for locking and sealing inside. The inner-locking type tube fitting has the effects that: firstly, the inner-locking type tube fitting is good in sealing effect in a product, does not have outer leakage hidden danger, is safe and reliable, is self-locked by a device on the blocking plug, does not need to open a pin hole in a tube fitting flange, keeps the integral integrity of the tube fitting flange, avoids the outer leakage hidden danger, and is safe and reliable in use; secondly, manufacturing difficulty of the tube fitting is reduced; and thirdly, mounting is convenient and quick.