Abstract: Facing the challenge of declining international competitiveness of agricultural products, the central government has encouraged farmers to expand the operation scale to achieve rapid development. With the development of large-scale agricultural operation, it raised different opinions on the definition of optimal operation scale and whether China’s grain production has achieved the optimal operation scale. Taking rice production in Jiangsu Province as an example, this paper applies the global DEA method to study the level of efficiency from the perspective of different sizes and the stage of agricultural development based on the micro-survey data. Results show that the comprehensive technical efficiency and pure technical efficiency were increasing. The pure technical efficiency of Jiangsu rice farmers was 0.87 in 2016, and the average pure technical efficiency of the rice farmers increased first and then decreased with the change of operation scale. In the optimal moderate scale range (3.22-4.83 hm2), the average pure technical efficiency reached the highest level to 0.891. At the same time, the pure technology efficiency of Jiangsu rice farmers showed differentiation and the concentration rate of farmers at higher level of pure technical efficiency showed a decreasing trend. Empirical tests show that the proportion of farmers at the stage of increasing returns to scale showed a decreasing trend in recent years. By 2016, 66.7% of the farmers have gotten rid of the sub-optimal scale, during which the farmers’ demand for scale expansion was very strong from the efficiency perspective and the grain production has achieved the optimal operation scale stage. To continue to increase agricultural productivity in the future, this paper suggests to popularize agricultural technologies, to develop agricultural social services, to unblock the market for land transfer, and to reform agricultural support policies.