Based on the data obtained from 9 long-term field experiments(1986～1999)in Hunan Province,difference in rice yield and soil fertility between paddy fields under different fertilization patterns was analyzed,with emphasis on effect of ratio of organic manure/chemical fertilizer on rice yield and soil fertility under the same N input condition.Results show that:based on averages over 13 years,Treatment NPK was 115.43% (early rice)and 68.20% (late rice),Treatment L-OM,128.45% (early rice)and 79.26% (late rice),and Treatment H-OM,122.87% (early rice)and 78.66% (late rice)higher than CK in yield.Mineral nutrients supply in the rice growth period is the key factor that leads to difference in rice production between different treatments.Compared with CK,Treatment NPK was obviously higher in soil nutrient content,indicating that chemical fertilizer does not only supply mineral nutrients to the crop,but also improve soil fertility.Treatment H-OM was higher than Treatment L-OM in soil nutrient content,suggesting that a high proportion of organic manure in fertilization has better effect on improvement of soil fertility.During the early monitoring period,the difference between Treatments L-OM and NPK in yield was widening, and then narrowing in the last few years.The difference between Treatment L-OM and H-OM always showed a narrowing trend, especially for late rice.All these suggest that yield difference varying with organic-inorganic fertilizer ratio is a temporary phenomenon and with the time going by and improvement of soil fertility,this difference will become narrower and narrower and even disappear.