Ningbo Seismic Station applied the P2000 radon measuring instrument to continuous gas radon observation experiment in Well ZK03 in its gas radon observation system，and recorded obvious tidal phenomenon and larger wave amplitude． The power spectrum estimate shows that there are significant tidal effects in the data observed． We also compared the dynamic water levels of the same well observation and VS vertical pendulum NS record to the tidal waveform and found the consistency in the curve variations: Both have two peaks and two valleys with about 2 hours in difference． The instrument has the function of the automatic deduction of background pollution， and can better reflect the dynamic change of radon process in underground fluid． The conclusion can be applied to the continuous earthquake fluid gas radon observation．