Various process control parameters for plasma polymerization such as different radio-frequency discharge power, monomer partial pressure, and deposition time are systematically tested for the deposition of polymethyl methacrylate (PMMA) thin films on glass. A thorough material characterization is carried out—the thickness and average deposition rate are evaluated by surface profiler; microstructures are examined by Fourier transform infrared spectroscopy; chemical compositions are accessed by X-ray photoelectron spectroscopy; and the wettability by water contact angle and surface morphology is inspected by atomic force microscope. In addition to the as-deposited PMMA films, some selected films are further treated by oxygen to modify their surfaces. These PMMA films are then used as substrates to culture human hepatocytes for testing their biocompatibility. Assessments on the results of cell culture by trypsin cell count, enzyme-linked immunosorbent assay, and MTT assay indicate that the human hepatocytes can proliferate and perform urea synthesis well on the deposited PMMA thin films regardless of oxygen treatment.