With control of the concentration of free ammonia (FA), shortened nitrification-denitrification was accomplished in SBR to achieve enhanced nitrogen removal from the sewage containing seawater. Several parameters which included salinity, temperature, pH and NH4(+)-N load were studied to evaluate their effects. The results of experiences indicated that shortened nitrification-denitrification can be accomplished in sewage containing seawater with relatively high salinity. With various salinity, the nitrogen removal efficiency had relationship with the NH4(+)-N load, there should be a lower NH4(+)-N load when the salinity was high. The nitrogen removal efficiency reached above 90% when the NH4(+)-N load was not exceed 0.15 kg/(kg.d). Elevation of the temperature availed to higher nitrogen removal efficiency, this efficiency doubled when the reaction temperature was changed from 20 degrees C to 30 degrees C. Relatively high value of pH, in the range of 7.5 and 8.5 had advantage to achieve effective shortened nitrification-denitrification which caused by the selective inhibition of free ammonia(FA).