Abstract: Based on the analysis of the structure and function of Direct Digital Frequency Synthesizer(DDS), an online measurement system for DDS is developed, which can test functional registers, capture output waveform and power supply current. Verification experiment has been carried out. The results show that the single event effect may cause waveform disturbances, functional interruption of the output waveform, and sudden increase of power current. We consider that the occurrences of single event transient in internal PLL of DDS and upset of functional registers are the leading causes of waveform disturbance. The DAC main function registers upset triggers the output waveform functional interruption, single event latchup causes current increase. This study provides a reference for consolidation and evaluation of domestic DDS devices.