Abstract: A Simplified dynamic model of relations between accumlating rate and national economy is established depending on the general economic principle.The model issolved by using the maxima principle of control theory and giving accordingly a set of optimal accumulating rates for various economic goals.It includes that (1) the optimal accumulting rate should be about 25.3%,if a rapid economic growth is the primary consideration;(2)the reasonable figures of accumulating rates should be always in the range of 23.3%～33.7%,whichever economical goal may be;(3)the accumulating rates should be assured to increase per annum with the appropriate figure at 29%,and the upper limit at 33.7%,if higher accumulating rate is the basic concern;(4)the accumulating rates should be assured to decrease per annum,withthe appropriate figure at about 23% and the lower limit at 21.3%,if higher comsumption is emphasized;(5)as a comprehensive trade-off among accumulating,comsumption and economic growth rates,the moderate accumulating rate should be inthe range of 23%～28%,the figure of 25.5% recommended.