Abstract: [Objective] To assess the economic benefit of alfalfa planting in a alfalfa planting park, locating in the national modern agricultural demonstration area of Tumed Left Banner, Hohhot City, Inner Mongolia, where the ′high-quality forage technology research project′ is implemented, so as to provide guidance for adjusting the planting structure and promoting the development of the alfalfa industry in this area. [Method] Data of six categories of input factors during alfalfa planting process in the surveyed alfalfa planting park, such as seed, pesticide and mechanical fuel oil, were collected. The primary and secondary output factors were regressed and evaluated using the Cobb-Douglas production function model. [Result] Among the six categories of input factors, the mechanical fuel oil and pesticide inputs had negative influences on profit of alfalfa planting in the primary output model, whereas the remaining inputs had positive impacts, with the seed input having a significant （P<0.05） impact. Seed, chemical fertilizer as well as water and electricity inputs all exhibited a positive connection with alfalfa yield in the secondary output model. The profit output model was: Y_output=4.532 503-0.265 386X_seed+0.638 345X_{chemical fertilizer}-2.988 071X_{water and electricity}+5.506 927X_{mechanical fuel oil}-2.662 652X_labor-2.895 284X_pesticide. The yield output model was: Y_output=18.740 580+1.415 616X_seed+0.252 048X_{chemical fertilizer}+0.371 124X_{water and electricity}+0.497 999X_{mechanical fuel oil}+0.060 733X_labor+0.184 595X_pesticide. The marginal yield of seed, chemical fertilizer, water and electricity, mechanical fuel oil, pesticide and labor inputs were 7.981, 0.472, 0.549, 5.301, 0.475 and 3.176 kg/hm², respectively. Mechanical fuel oil accounted for the highest percentage （44.59%） among the input factors in alfalfa planting. Planting of alfalfa experienced a gradually growing stage of scale reward. The marginal yield of alfalfa seed and mechanical fuel oil inputs was significantly larger than zero. Alfalfa production could be improved by increasing these two inputs. [Conclusion] In this area′s alfalfa production practices, the seed, pesticide and mechanical fuel oil inputs should be boosted, while the other input factors should be kept under control.

Key words: alfalfa industry, Cobb-Douglas production function, economic benefit analysis, Hohhot City