  The isoscaling behavior is investigated in the frame of Isospin dependent
Quantum Molecular Dynamics (IQMD) models. The isotopic yields ratio $Y_2$/$Y_1$
for reactions $^{48}Ca$+$^{48}Ca$ and $^{40}Ca+^{40}Ca$ at different entrance
channels are simulated and presented, the relationship between the isoscaling
parameter and the entrance channel is analyzed, the results show that $\alpha$
and $\beta$ reduce with the rise of incident energies and increase with the
impact parameter b, which can be attributed to the temperature varying of the
pre-fragments in different entrance channels. The relation of $\alpha$ and
symmetry-term coefficient $C_{sym}$ reveals that the chemical potential
difference $\triangle\mu$ is sensitive to the symmetry-term coefficient
$C_{sym}$.
