With the continuous maturity of tidal current power generation technology, the scientific requirements for testing and evaluation are also increasing. In the process of analyzing the measured power data of tidal current power generation, the selection of sampling interval has a significant impact on the accuracy of power fluctuation analysis. Choosing an appropriate sampling interval can reduce data processing and improve calculation speed while ensuring the accuracy of test data. Based on the measured power data of tidal current power generation in a certain sea area of China during rising and falling tides, this paper calculated and analyzed the power fluctuation of multiple sampling intervals through discrete index analysis and first-order difference component analysis. And based on the entropy weight method, obtained the regularity of power fluctuation with sampling interval, calculated the comprehensive fluctuation coefficient to determine the maximum sampling interval, and proposed a recommended sampling interval of 60 seconds. This has important practical significance for scientifically testing tidal current power generation.