The utility model discloses a coal -fired unit SCR reactor flue gas sample thief, which comprises a housin, the preceding terminal surface right side of casing is equipped with the display screen, and the lower right corner is equipped with the sampling interface, the side is through fixed axle swing joint handle about the casing, the sampling interface passes through pipe connection condensation filtration system, condensation filtration system passes through pipe connection flue gas change of current system, flue gas change of current headtotail oscilloscope, multi -functional vector wave filter is connected to oscilloscope's output electricity, signal processor is connected to the output electricity of multi -functional vector wave filter. This coal -fired unit SCR reactor flue gas sample thief, sampling interface connection titanium alloy sampling pipe is sampled through the titanium alloy sampling pipe, has high temperature resistant, corrosion resistance, is fit for long -term sampling, utilizes oscilloscope, multi -functional vector wave filter, spectral analyser cooperation to use and can accurately utilize image, characters branch to appear the material content of flue gas, and overall structure is simple, convenient operation.