The invention provides a method and device for determining the downhole liquid level depth of a pumping well. The method comprises the steps that the wellhead temperature, wellhead casing pressure and wellhead oil pressure of an oil well to be measured are obtained; according to the wellhead temperature, the wellhead casing pressure and the wellhead oil pressure, the propagation speed of a sound wave in the oil well to be measured is determined, transmission parameters of a sound pulse in the oil well to be measured are obtained; and according to the propagation speed and the transmission parameters, the downhole liquid level depth of the oil well is determined. According to the scheme, the technical problem that in an existing process, the fixed propagation speed is adopted to determine the downhole liquid level depth of the pumping well, and the inaccurate result is caused is solved, the technical effect of improving the accuracy of the propagation speed of the sound wave is achieved, and accordingly the accuracy of the downhole liquid level depth of the pumping well is improved.