By using the method of pot culture experiment in the case of artificial climate the result indicated that the effects of light intensity(X₁)and N application(X₂) on lettuce yield(y)were mathematically represented by the following equation in this study: y=-0.375+0.0230X₁+9.421X₂+0.0251X₁X₂-0.131×10^-4X₁²-17.794X₂²;The efficiency of N fertilizer was influenced by light intensity. A quadratic multinomial equation y=b₀+b₁X + b₂X₂, could be used to describe the correlation between N application and lettuce yield. Also, quadratic or cubic multinomial equation could be used to describe the correlation between light and lettuce yield. Accordingly, the effects of light intensity(X₁)on N application (X₂) were mathematically represented by the following equation: X₂=0.446-0.477×10^-2X₁+0.269×10^-4X₁²-0.394×10^-7X₁³. Moreover, nitrogen nutrition of lettuce was bigger influenced by light and N application.