Abstract: Taking lettuce（Latuca sativa L.cv.‘Flandria’）as experimental materials, the method of substrate culture was used, in order to study the effect of chelating calcium（EDTA-Ca） on growth of lettuce in greenhouse and investigate the feasibility of chelated calcium replacing free calcium ions as the calcium source of nutrient solution, which could avoid decreasing the availability of calcium fertilizer in nutrient solution.The results indicated that there were no significantly difference in shoot fresh weight and quality among treatments T1,T2 and control.The commodity character of lettuce was also good for the treatments T1 and T2.With the increasing of EDTA-Ca concentration in nutrient solution, the SPAD value of lettuce was increased, but the accumulated transpiration, shoot fresh weight and nutrient solution use efficiency were significantly decreased.Therefore, when the EDTA-Ca could be used as calcium fertilizer source for nutrient solution making under soilless culture condition, the concentration of EDTA-Ca should not be higher than 20 mg·L^-1 to avoid reducing the yield and nutrient solution use efficiency.