Auxiliary galleries are always adopted in long tunnel construction so as to shorten the construction period. The construction of the connection section between auxiliary gallery and main tunnel is difficult and the arrangement of it affects the tunnel construction obviously. The characteristics of 3 different construction schemes of connection section between horizontal gallery and main tunnel of Ping’an Tunnel on ChengduLanzhou Railway are summarized. The results show that the schemes of adding branch tunnel and enlarging construction of horizontal gallery step by step is superior to the scheme of direct enlarging construction of horizontal gallery.