A vector regression（VAR） model is constructed to describe the period-decoupled price sequences. Because all prices in next-day are determined at the same time， the period-decoupled price sequences are compatible with the market rules. Using the prices data of New South Wales in Australia's National Electricity Market， a VAR model is confirmed validity through augmented Dickey-Fuller test， and Box-Pierce Q statistics test. A structure analysis based on the presented model is investigated including Granger-causality and impulse response analysis. It is discovered that any variable omitted in the price model would reduce the forecast accuracy by Granger-causality test. Moreover， the impulse response analysis reveals that the prices in various hours have a different impact on the price of other hours， that is， the price fluctuation in peak periods has the greatest impact on the price in the other hours， and the price in off-peak periods is mostly affected by the price impulse of other hours.