Abstract: The experiment was carried out in the Wuqiao experiment fields of China Agricultural University from Oct. 1997 to Apr. 1998, to study the effects of nitrogen, phosphate, and potassium fertilizer applications on the economic benefit of forage rye and to optimize the fertilizing scheme. Mathematical models were established for the economic benefit of rye production with the treatments of N, P, and K fertilizer in this study. To gain more economic benefit, it was necessary to reduce fertilizer doses to control the cost of rye production when the price of rye hay was low and increase fertilizer doses to improve the yield of forage rye when the price of rye hay was high. The amount of fertilizer application should be determined by the integration of several targets, including the maximum yield, economical considerations, and quality. Higher fertilizer application is best for obtaining maximum yield but strategies to use moderate amounts of fertilizer are more economical. For obtaining higher quality, more nitrogen fertilizer is required. These three targets were compromised only by the price of forage rye. In general, the optimum combination of N, P, and K was 225 kg/ha N, 75 kg/ha P₂O₅, 30 kg/ha K₂O.