Abstract: Agricultural mechanization makes contribution to agricultural production, which brings about the production increment resulting from increasing invented farm machinery and from raising the productivity of farm machinery. The contributing ratio can be measured with the proportion of the coefficient of machinery output elasticity in the sum of those of all factors' output elasticities. The quantity of farm machinery's contribution to raising labor productivity is decided by the quantity of its contribution to the production increment and of its substitution for labor force. And that to rural economy is in direct proportion to the growth rate of labor productivity resulted from farm machinery, the ratio of nonagricultural output value to rural GDP, the number of labors engaging in agriculture.