The invention provides a sensitivity measuring device and method applied to an ultra-wideband sampling receiver, wherein the device includes: a display unit, a control and a processor, a first frequency adjustable constant temperature crystal oscillator, a second frequency adjustable constant temperature crystal oscillator, a frequency difference Detection, emission timing formation circuit, ultra-wideband signal generation circuit, frequency band controller, amplitude controller, first AD acquisition circuit and second AD acquisition circuit, the method includes the following steps: S1, using a frequency-adjustable constant temperature crystal oscillator, respectively producing two S2, one of the square wave signals is directly transmitted to the receiver under test, and the other is used as a time reference, and is transmitted to the receiver under test after processing; S3, the receiver under test outputs an intermediate frequency signal, when the signal-to-noise ratio reaches 1 When :1, the amplitude of the currently injected UWB impulse pulse is the sensitivity value of the receiver under test. The invention solves the difficulty of measuring the sensitivity of the ultra-wideband sampling receiver, and has the advantages of simple operation and low cost.