The invention belongs to the technical field of high-temperature smoke temperature measurement and especially relates to an ultrasonic-based boiler furnace smoke temperature measuring device. The device comprises a computer, a junction box, a left ultrasonic transducer, a right ultrasonic receiver, a signal conditioner and a double-channel data collection card. The left ultrasonic transducer and the right ultrasonic receiver are arranged symmetrically on the furnace walls at the two sides of a boiler furnace, and are connected with the signal conditioner; the signal conditioner is connected with the double-channel data collection card; the double-channel data collection card is connected with the computer through a USB cable; and the left ultrasonic transducer is connected with the computer through the junction box and receives an ultrasonic signal sent by the computer. The device is not limited by high-temperature, dusty, corrosion and turbulence complex hostile environments and the like in the furnace, has the advantages of non-plug-in, accurate, real-time and portable measurement and the like, can judge combustion condition of a boiler time and is convenient to adjust and control.