Great difficulties will occur at tunnel breakthrough when collapse happens. In order to guarantee the construction safety of tunnel breakthrough and to avoid secondary collapse, the key points and difficulties of breakthrough construction of Fengling Tunnel on NanchangNingdu Highway in Jiangxi are analyzed; the systematic processing technologies, including comprehensive geophysical prospecting, piperoof grouting support of collapse section, decision of rational tunnel breakthrough crosssection, piperoof grouting support of breakthrough section and shortdistance excavation and strengthened support of tunnel, are proposed; the stress and displacement of surrounding rocks and primary support during construction are numerically simulated by means of 3D numerical simulation method. The monitoring results show that the technologies used are safe and feasible.