In order to measure the gas and liquid flow rates of the wet gas on line not separation, this paper develops a wet natural gas two-phase computation system, which accompanies with the dual throttling wet gas flow meter as a secondary instrument. This flow computation system is based on ARM9 embedded system with the Linux OS and is powered by a solar power system. A hardware and software platform of a secondary instrument working for the flow rates computation is constructed for unattended operational natural gas wells. The signal acquisitions of the pressure, differential pressure, temperature, and the calculation of two phase metering model have been actualized. In addition to the basic function, the system provides display, storage, and historical data inquiry of the instantaneous and accumulative flow rates, as well as the GPRS wireless communication. It has already been trial run at some unattended operational wellheads for the gas and liquid metering of the wet gas.