Abstract: The objective of this study was to study the interactive effects of elevated CO2 and various strengths of nutrient supply on the dynamic of the growth and N,C accumulation in tomato seedling stage under hydroponic cultivation for 55 days.The CO2 concentration in the growth chambers were set as 360 μL/L and 720 μL/L respectively.The results showed that the elevation of CO2 significantly accelerated the growing speed and increased the biomass accumulation of the tomato seeding at all sampling periods,but their response to CO2 enrichment strongly depended on the strength of nutrient supply.The increased extent went up along with the increase of nutrient concentration.Elevated CO2 increased C and N accumulated rate,and C and N uptake rate in tomato seedling leaves at all sampling periods,the higher nutrient solution concentrations and the higher elevation.C and N accumulated rate and C and N uptake rate appeared an upward tendency with the prolongation of growing period.This indicated that fertilizer application rate must be increased at later growth stage,furthermore,the application rater should be higher under elevated CO2.The ratio of C and N response to elevated CO2 was different at different growth stage under different nutrient solution treatments.At the same CO2 concentration,the ratio of C and N became increased along with the decrease of the nutrient solution concentration.The experimental(results) indicated that the correlation between C and N accumulated amount,C and N absorbed rate and growth time all fit the conic equation.