The utility model discloses a boiler steam -temperature control system, including over heater group and re -heater group, the superheated steam of over heater group and re -heater group and the partial steam of reheat steam export are connected to low temperature water heat exchanger, low temperature water heat exchanger connects in parallel in the economizer, when overheated vapour passes through over heater group, not only through overheated desuperrheater, still the part inserts low temperature water heat exchanger, when reheat vapour passes through re -heater group, not only through the reheat desuperrheater, still the part inserts low temperature water heat exchanger, feeding water, some passes through the economizer, partly low temperature water heat exchanger that gets into, carry out the heat transfer to superheated steam and reheat steam respectively in low temperature water heat exchanger, final and economizer export joins flow direction subordinate heater. The utility model discloses the be heated heat transfer volume of interfacial of differences such as radiation, convection current can be adjusted to can balanced difference the be heated temperature of interfacial, improves the adaptability of coal, load, energy loss among the reduced temperature accommodation process.