The spectrum analysis and sine wave curve fitting are the most common methods used for ADC dynamic performance tests. But if the SNR of signal source is lower than ADC system, there will be a bigger deviation in the test result. A new method is proposed to test dynamic performance. This method can eliminate the influence of signal source, through which the dynamic performance of high-resolution ADC can be tested with a conventional signal source. The simulation proves the validity of this method. Finally, the test result of an ADC system is given.