Abstract: Global potassium resources and production capacity are relatively concentrated, and the consumer market is separated from the place of origin, resulting in nearly 80% of global potassium fertilizer production to be sold to the main consumer market through trade.As a tradable commodity, whether the international potash fertilizer market conforms to the law of one-price or not, this paper uses different methods to verify whether the price of the international potassium fertilizer market supports the hypothesis of the law of one-price, so as to examine the degree of spatial integration of the international potassium fertilizer market.Based on the research findings, there is a very significant price co-movement feature in the international potassium fertilizer market, and the price correlation degree of the export market is significantly higher than that of the import market; the law of one-price hypothesis has been verified mainly among the import market of potassium fertilizer and between the import market and the export market, while the law of one-price hypothesis has not been supported among the export market of potassium fertilizer.