The utility model discloses a CEMS extraction formula smoke and dust appearance constant speed sampling device suitable for change operating mode, including pitot tube, adc, signal line, PLC module, frequency conversion fan, smoke and dust analytical equipment, heat tracing pipe, sampling rifle, heating device. The utility model discloses an advantage does: utilizing introduction flue gas velocity parameter to adjust smoke and dust appearance extraction speed, can realizing the constant speed sampling to flue gas in the flue, improve the accuracy of smoke and dust sample, especially work as the operating mode and change, when the interior flue gas velocity of flue was constantly changeable, this kind of smoke and dust appearance was more obvious for ordinary smoke and dust appearance advantage.