Combined connecting pipe and connecting method thereof

The invention relates to a combined connecting pipe and a connecting method thereof. The combined connecting pipe comprises a connecting inner pipe and a connecting sleeve, wherein the connecting inner pipe is integrally formed and comprises an inner sleeve area, a buffer area and an outer pipe area; the outer diameter of the outer pipe area is consistent with the outer diameter of the connecting sleeve; the outer diameter of the inner sleeve area is smaller than the inner diameter of the connecting sleeve; one end of the buffer area is connected with the inner sleeve area, and the other end of the buffer area is connected with the outer pipe area. According to the combined connecting pipe, the coaxiality of the connecting inner pipe and the connecting sleeve is good, welding of a support rod is facilitated and the efficiency is high; the combination strength is high, and the integral rigidity can be further improved; more effective connection is realized in comparison with a previous butting mode, such that