Pot experiments were carried out to study the effect of combining application of organic manure (silkworm manure) and inorganic fertilizer (urea and ammonium bicarbonate) on the biomass-N and N-supplying characteristics of coastal slightly saline soil. The results obtained showed that(1)application of both organic and inorganic fertilizers could significantly increase the soil biomass-C and biomass-N and the combining application of silkworm manure and inorganic fertilizer might cause a more increase of biomass-N than single application of silkworm manure or inorganic fertilizer; (2) soil biomass-N was an important link in soil nitrogen transformation and a major part of available N in soil; (3) there was a significantly close relationship between the changes of soil biomass-N and soil N-supplying characteristics, thus a strong immobilization of N fertilizer by microorganisms was always followed by a net N mineralization, which was most favourable for the growth and development of barley plant; and (4) silkworm manure was helpful in raising fertilizer utilization efficiency, especially for ammonium bicarbonate which can volatilize violently in coastal saline soil because of its higher pH, and it would be an efficient way to raise N utilization efficiency by combining application of various organic manures and inorganic fertilizers.