Most, if not all, of the existing theore-tical studies dealing with the linkage between macroeconomic variables and agricultural product prices are concerned with closed economies. This paper instead constructs an open-economy model under fixed exchange rates. The model we set up includes the agricultural market, the non-agricultural market, the money market, and the foreign exchange market. Based on this open-economy model, we study the characteristics agricultural product prices will exhibit when the monetary authorities engage in a pre-announced monetary policy. Two main conclusions emerge from the analysis. Firstly, the expansion of domestic credit will not affect agricultural product prices, but induce the level of foreign exchange reserves decrease to the same extent as domestic credit. Secondly, agricultural product prices rise process during the period following the announcement but prior to the monetary expansion, while they decline after policy implementation.