The small open economy with currency substitution environments. Analysis (1) Currency substitution (complementary) will affect the balance of the local uncertainty. (2) Nominal domestic currency the growth rate of prices the rate of expansion impact. (3) Nominal domestic currency the growth rate of on the balanced growth rate impact. We are find that (1) local indeterminacy is more likely to appear if the case of currency complementary. (2) When the currency substitution (complementary) to improve the growth rate of nominal domestic currency expansion will make the price rise (fall) is a high possibility. (3) When currency substitution (complementary) to improve the nominal growth rate will make capital of its currency, the real growth rate of its currency decline (rise) is a high possibility.