The invention discloses an adapter of a network voice telephone system for connecting a fixed telephone network and a fixed telephone to a PC. The adapter comprises an MCU controller body, a flip cover, an insertion cover, cooling fins, a dustproof net, a fan, an adhesive layer and a positioning rod. The flip cover is arranged at the top end of the MCU controller body, the fan is mounted in a groove, and the insertion cover is mounted at the other end, close to the outer side of the fan, of the MCU controller body in a sleeving manner; the dustproof net is mounted in the insertion cover, and the upper flexible glue is installed in a clamp; the positioning rod is mounted at the bottom end of the flip cover, and the adhesive layer is mounted at the bottom end of the MCU controller body. Theadapter is scientific and reasonable in structure and is safe and convenient to use; by arranging the cooling fins and the fan, the heat dissipation of the MCU controller is facilitated; by arrangingthe double-layer flexible glue, the dust can be prevented from entering the wiring ports; by arranging the dustproof net and the insertion cover, the installation of the dustproof net is facilitated;by arranging the positioning rod and a slot, the disassembly of the MCU controller is facilitated; and by arraning the adhesive layer, the fixing of the MCU controller is facilitated.