Digital frequency analyzers are commonly used in FRF (Frequency Response Function) measurement using impact force method. The analyzers are inevitably generating errors due to limited spectral line as well as frequency span. The FRF magnitude error has been derived by Partogi  theoretically. This paper describes numerical simulation used to validate the theoretical equation. For this purpose, three numerical case studies have been simulated. Based on the results of simulation, the FRF magnitude errors can then be calculated and compared to those obtained from theoretical equation. The results show a perfect match between them so that, it can be concluded that the equation has been derived properly.