Price dispersion serves as a crucial indicator for measuring market integration, providing a novel perspective for studying the unified national market. Through collecting daily price data of identical products from different platforms, this study measures the degree of price dispersion in China. The findings reveal: (1) The overall level of price dispersion in Chinas online market remains relatively high, with significant heterogeneity observed across different product categories. The constructed highfrequency price dispersion index (iPDI) indicates that a lower index value suggests higher market integration, while a higher value implies lower integration. (2) Price variance decomposition analysis reveals that price dispersion primarily stems from crossplatform competition. Furthermore, empirical modeling demonstrates an inverted Ushaped relationship between crossplatform competition and price dispersion. (3) Applying microscopic measurements of price dispersion at the macroeconomic level, the Consumer Price Index (iCPI_pd) compiled based on price dispersion characteristics more accurately reflects the fluctuation patterns of commodity prices.