  We propose an effective phonon treatment in one dimensional
momentum-conserved lattice system with asymmetric interparticle interaction
potentials. Our strategy is to divide the potential into two segments by the
zero-potential point, and then approximate them by piecewise harmonic
potentials with effective force constants $\tilde{k}_L$ and $\tilde{k}_R$
respectively. The effective phonons can then be well described by
$\omega_c=\sqrt{2(\tilde{k}_L+\tilde{k}_R)}% |sin(\frac{1}{2}aq)|$. The
numerical verifications show that this treatment works very well.
