Poly(L-lysine) (PLL) was end-grafted onto silicon oxide surfaces to study its conformational transition among alpha-helix, beta-sheet, and random coil at the solid-water interface. Surface-grafted PLL films were prepared from surface-grafted poly(N-epsilon-carbobenzyloxy-L-lysine) (PCBL) thin films, which were fabricated by the surface-initiated vapor-deposition polymerization (SI-VDP) of N-carboxyanhydride (NCA) of N-epsilon-carbobenzyloxy-L-lysine. The reaction parameters during the SI-VDP process, including NCA concentration, substrate temperature, and reaction time, were optimized in order to synthesize homogeneous PCBL films with well-controlled thickness. Under the optimal conditions (substrate temperature at 105 degreesC, NCA evaporating temperature at 100 degreesC, and 8 mg of NCA at 0.1 Pa), alpha-helical PCBL films with thickness ranging from 4 to 120 nm can be synthesized by controlling the reaction time from 5 to 120 min. The conversion from PCBL to PLL was accomplished by removing N-epsilon-carbobenzyloxy groups in the hydrogen bromide/benzene solution with the aid of ultrasonication for 40 min. The surface-grafted PLL films with an estimated DP of 750 exhibited versatile conformations among alpha-helix, beta-sheet, and random coil depending on the external environments. The conformational transition from one state to another was successfully induced by external stimuli, such as pH (H+/OH-), surfactant (sodium dodecyl sulfate (SDS)), and anion (ClO4-). In the process of the conformational transition, macroscopic properties such as thickness, refractive index, and wettability changed correspondingly. For example, a surface-grafted random-coiled PLL had a film thickness of 215 nm and a refractive index of 1.37 at pH 7, whereas it changed to a beta-sheet conformation when binding with SDS, with the film thickness shrinking to 145 nm and the refractive index increasing to 1.45. Compared to the free PLL chains, the stability of the helical state increased when the PLL chains were densely immobilized on the surfaces. The transitional behaviors were characterized by Fourier transform infrared spectroscopy, circular dichroism spectroscopy, and ellipsometry.