The invention relates to a system used for recovering the waste heat of smoke and heating heat supply network water or condensation water through the horizontal type phase change technology and a control method thereof. The system comprises a flue, an evaporation heat exchanger, an ascent pipe header and a descent pipe header, wherein the evaporation heat exchanger is arranged inside the flue and is provided with the ascent pipe header and the descent pipe header; the system is characterized by further comprising a double-effect phase-change heat exchange steam drum, a first heat exchange tube bundle and a second heat exchange tube bundle. According to the control method, the smoke flows through the evaporation heat exchanger along the flue, the waste heat of the smoke heats condensation working media inside the evaporation heat exchanger for generating steam, the steam enters the double-effect phase-change heat exchange steam drum through the ascension pipe header, the descent pipe header and an ascent pipe port. According to the system and the control method thereof, the waste heat of the smoke can be recovered, the heat supply network water and the condensation water can safely and stable be heated for a long time, and the energy-saving benefit can be maximized.