Conformational properties and elastic behavior of protein-like chains are investigated using the protein-like lattice model built by Kolinski et al．Here the sequence of (HHPPHPP)x is adopted

and different chain length and different α helical interaction energy are also considered．It is found that the α helical interaction energy directly influences the interior conformation and elastic behavior of protein-like chains in the process of tensile elongation． The chains with large α helical interaction energy have lower energy and less elastic force

and they are more easily to lose contacts and more easily to take the“rod”structure．Moreover. α heheal structure remains unchanged in the process of tensile elongation．In the meantime

the length of chains also influences the conformational properties of chains in the elongation process．The long chains have lower energy

less elastic force

more Helmhaltz energy

and larger number of contacts．However

they are mole difficult to take the“rod” structure．This investigation can help us to understand the interior conformations and elastic behavior of real proteins in the process of elongation．