Studies were carried out on B radford reactive soil protein(BRSP) concentrations in aggregates different in particle size and relations of BRSP with soil organic C and total N in fields of long-term fertilization experiment under a continuous rice-rice cropp ing system.At the same time,in order to simplify the process of the soil BRSP test,attempts were made to exp lore feasibility of determining soil BRSP concentration using whole soil passed through 1 mm sieve instead of 1～2 mm soil aggregates.Results show that long-term fertilization significantly affected concentrations of soil total BRSP(T-BRSP) and easily extractable BRSP(EE-BRSP) in 1～2 mm aggregate.Soil BRSP was increased sharply by application of inorganic fertilizer p lus organic manure,especially in the treatment of N,P,K p lus rice straw.After 25 years of continuous fertilization,regardless of treatments,both T-BRSP and EE-BRSP in 1～2 mm aggregates were highly correlated with SOC and TN.It was found in the experiment that BRSP existed in < 1 mm aggregates and showed a tendency similar to what the aggregates did in variation from treatment to treatment.It was also discovered that it is feasible to determine soil BRSP using the whole soil passed through 1 mm sieve,because both T-BRSP and EE-BRSP in the whole soil are highly correlated not only with those in 1～2 mm aggregates,but also with SOC and TN in the soil.