Abstract: By adopting the double optimal value method，the annual optimal amount of nitrogen fertilizer and the ratio of nitrogen fertilizer distributed among crops in the system of wheat relay intercropping with corn and peanut is studied in sandy soi1．The results show that the annual optimal total amount of nitrogen fertilizer applied in this system is 311．1 kg／hm² and the suitable distributive proportion of the fertilizer is 33．7：35．1：31．2 among the three crops．It indicates that the applying amounts are 104.8 kg／hm² ，27.3kg／hm² and 72．8kg／hm² in natural area for wheat，corn and peanut respectively．and the annual amount fertilized is 204．9kg／hm² per natural hectare Though it decreases by 29．9％ eompared with the rate determined by conventional fertilization for each so1e crop．the yields of wheat．corn and peanut and total yield gained increase by 9．3％,3．7％ ,4．8％ and 6．3％ respectively．