Tsunami waveforms contain the features of its source, propagation path, and local topography. On 4 March 2021, two tsunamis were generated by earthquakes in the Kermadec Islands, New Zealand, within 2 h. This rare case gives us a valuable opportunity to study the characteristics of two tsunamis. We analyzed the records of two tsunamis at tide gauges with spectral analysis tools. It is found that two tsunamis superpose during the few hours after the arrival of the second tsunami.