In order to understand the genetic contribution of six agronomic traits to yield, 14 flue-cured tobacco varieties (or breeding lines) and their 41 F1 crosses were used for multivariable conditional analysis. The contribution of additive variance of plant height to yield was larger than other agronomic traits. The largest contribution of dominant variance to yield was due to the length of middle leaves. All agronomic traits investigated had small contribution to yield due to additive x environment interaction effects and dominant x environment interaction effects. No identical trait of different parents showed the largest contribution to additive effect of yield. This could be resulted from the fact that each parent had its own genetic and developmental characterization. The dominant effects of yield were mainly influenced by length of middle leaves in most crosses. Length of middle leaves could be served as ameasurement to indirectly select the cross parent having high dominant effect of yield.