Three-dimensional Monte Carlo simulations of comb-like polymer chains with various backbone lengths N b, arm lengths N a and arm densities m are carried out to study the elastic behavior of comb-like polymer chains. The radius of gyration, the shape factors and bond length in different cases during elastic process are calculated, and it is found that the comb-like polymer molecules with longer backbone or shorter arm are more close to linear chains. But the arm density m affects the chain conformation non-monotonously. Some thermodynamic properties are also studied. Average Helmholtz free energy and elastic force f all increase with elongation ratio λ for all chains.