The acquisition of dynamic analog-to-digital converter (ADC) parameters is becoming increasingly relevant as electronic information develops at a rapid pace. The fundamental challenge of the spectrum test for ADC is that coherent sampling is difficult to achieve, especially because of the high accuracy of the excitation signal necessary for coherent sampling. Therefore, incoherent sampling is certainly unavoidable in the actual test. If the coherent sampling condition is not reached in the test, spectrum leaks from test data after Discrete Fourier Transform (DFT) analysis, resulting in inaccurate parameters. In this study, a new breakdown and reconstruction method was presented using the Ensemble Empirical Mode Decomposition (EEMD); Hilbert transform and parameter fitting method can accurately estimate the incoherent fundamental and harmonic waves, then reconstruct them to obtain accurate ADC dynamic parameters.