The chain stiffness is an important characteristic that affects the properties of many biological and synthetic polymers. We develop a perturbation theory in the framework of a Green's-function approach to treat the chain stiffness effects systematically. This scheme incorporates the standard flexible-chain Edwards equation in the zeroth order. When applied to the chains on the surface, the theory predicts novel features in adsorption-desorption transitions coupled with types of isotropic to nematic ordering transitions, giving a rigorous quantitative basis for our previous scaling theory results. We analyze the phase diagrams, and various quantities that detail the chain distribution including orientation-order-parameter distribution of the adsorbed semiflexible polymers. (C) 1997 American Institute of Physics.