One-dimensional simulation of laminar diffusion flame is performed both in physical and mixture-fraction (Z) space, and the relation between their flamelets are investigated. The strain rate, which characterizes the flamelet behavior in physical space, is converted into scalar dissipation rate and the combustion properties are transfered to Z space. The results show that the behaviors of the flamelets under the assumption of unity Lewis number for Z space calculation are in general agreement with those for physical space calculation. For the Z space calculation, non-unity Lewis number condition leads to the expansion of the extinction limit and the decrease of the peak temperature. As a results, the distributions of the temperature and mass fractions with Z deviate from those for Z space calculation with unity Lewis number assumption and physical space calculation.