Abstract: A joint assembly on a front frame tube of a baby stroller is revealed. The front frame tube includes an upper tube part and a lower tube part while the joint assembly consists of a first part, a second part and a connection part. The first part and the second part are respectively sleeved and connected with the upper tube part and the lower tube part while the other end of the first part and of the second part is connected with the connection part. Moreover, a leaning support surface for leaning against the first and the second parts is formed in a slot of the connection part. Thus the upper and the lower tube parts are stopped by the leaning support surfaces when being extended while the first part and the second part are also supported. Therefore, the front frame tube is maintained and fixed in an extended state.