The conformational properties and elastic behaviors of protein-like single chains in the process of tensile elongation were investigated by means of Monte Carlo method. The sequences of protein-like single chains contain two types of residues: hydrophobic (H) and hydrophilic (P). The average conformations and thermodynamics statistical properties of protein-like single chains with various elongation ratio l were calculated. It was found that the mean-square end-to-end distance r increases with elongation ratio l. The tensor eigenvalues ratio of : decreases with elongation ratio l for short (HP)x protein-like polymers

however

the ratio of : increases with elongation ratio l

especially for long (H)x sequence. Average energy per bond increases with elongation ratio l

especially for (H)x protein-like single chains. Helmholtz free energy per bond also increases with elongation ratio l. Elastic force (f)

energy contribution to force (fU) and entropy contribution to force (fS) for different protein-like single chains were also calculated. These investigations may provide some insights into elastic behaviors of proteins.