The invention discloses a device and a method for measuring the characteristic impedance and the complex wave number of an acoustic material. The device comprises an acoustic tube, an impulsive sound source, a microphone, a power amplifier, a signal conditioner, an adapter and a data acquisition device, wherein the acoustic tube consists of a section of large-diameter cylindrical tube, a conical tube and a small-diameter cylindrical tube which are fixedly connected with one another coaxially; three through holes which are vertical to the center axis of the small-diameter cylindrical tube are formed in the side wall of the small-diameter cylindrical tube; the impulsive sound source is arranged in the large-diameter cylindrical tube; and a back cover is in threaded connection with the outer end of the small-diameter cylindrical tube. The method comprises the following steps of: firstly, acquiring a frequency response function of a whole measuring system; secondly, acquiring required excitation signals of the impulse sound source, and exciting the measurement of the impulsive sound source to obtain sound pressures and vibration velocities of front and rear end surfaces of a sample to be tested; and finally, calculating the characteristic impedance and the complex wave number of the sample to be tested. By adopting the method, the problem that the measurement at a low-frequency band is not accurate enough when the characteristic impedance and the complex wave number of a high-flow-resistance material are measured by using the conventional double-cavity method and the conventional double-thickness method is solved.