It has been an important issue to analyze the possible impact of macroeconomic effects, such as: exchange rate or interest rate, on the commodity prices since 1970s because of the tremendous volatility of commodity prices on the US. Thereafter, there are a lot of literature in agricultural economics relative to the empirical study. But the results of these literature are ambiguous. On the other hand, Blandchard (1981) incorporated the stock market into the traditional IS-LM model and discussed the interaction between stock market and economy. The financial sector plays an important role to affect the time path of commodity prices it cannot be ignored since agricultural industry is just one of sector among the whole economy. The main purpose of this article is to add the stock market into the two-goods economy. One is commodity product and the other is nonagricultural product. According the model including commodity market, nonagricultural product market, monetary market and stock market and under the assumptions of perfect substitutes between stock and bond and perfect foresight expectation, the effect of stock market policies, such as financing interest rate, financing ratio, on dynamics of commodity and share prices will be analyzed. The result shows that in the long run the impact of stock policies on commodity prices depends on the relative magnitudes of price effect of commodity and interest rate effect. While in the short run, whether share price overshooting or not it depends on the length of time between announcement and implement of policies.
