A plug-in wire connection terminal structure includes a main body having a receiving space. A lateral side of the receiving space is formed with an arched guide slot. A holding plate has a receiving section formed with a wire entrance and a conductive contact section formed with a socket. An annular wall of the socket is formed a slit. A small-diameter fitting section is disposed at an outer end of the conductive contact section. A collar member is tightly fitted on the fitting section. A connection section is disposed on the receiving section. A leaf spring has a bight section received in the arched guide slot. One end of the leaf spring is formed with a connected section latched with the connection section. The other end of the leaf spring is formed with an abutment end obliquely extending the receiving section.