Abstract: Management performance is closely related to farmers’ management capability; while agricultural technical training is an important policy tool to improve the management capacity of farmers. Therefore, the integration of technical training into the analytical framework of the relationship between farm operation scale and farm income will help to grasp the income growth mechanism of scale economics in farming. Based on a survey data of 360 family grain farms in Jiangsu, this paper investigates the relationship among farm operation scale, agricultural technical training, and farm income from the perspective of net income per unit area, and tests the mediation effect of technical training. Results show that the relationship between farm operation scale and farm income is an inverted “U” shape: the highest net income per hectare is in the 6.67~13.33 hm2 scale range. Calculation shows that the optimal scale of the sample farm is 8.5 hm2, and before the optimal scale, each additional hectare of farm operation will improve income by 1.7%. Agricultural technical training has a significant impact on farm income with influence coefficient of 0.031. At the same time, agricultural technical training also has a positive mediation effect on the relationship between farm operation scale and farm income. Therefore, this paper suggests that the government should strengthen the construction of farmland circulation market to realize moderate scale effect. Meanwhile, cultivating family farms with proper operation scale should be combined with agricultural technical training.