A tube connection assembly of a bicycle frame includes a bi-forked portion formed by a hollow rectangular tube; one end of the rectangular tube being bi-forked as two halves; each half having a positioning groove; and a combining portion formed by two plates which are connected as a shape corresponding to that of the positioning groove and the bi-forked portion so that in assembly the combining portion is assembled to the bi-forked portion; and connection area of the bi-forked portion and combining portion being welded.